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Physics GRE GR8677 Solutions
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DRAFT
The Physics GRE Solution Guide
GR8677 Test
http://groups.yahoo.com/group/physicsgre_v2
November 3, 2009
Author:David S. Latchman
DRAFT
2
David S. Latchman ©2009
DRAFTPreface
This solution guide initially started out on the Yahoo Groups web site and was prettysuccessful at the time. Unfortunately, the group was lost and with it, much of the thehard work that was put into it. This is my attempt to recreate the solution guide andmake it more widely avaialble to everyone. If you see any errors, think certain thingscould be expressed more clearly, or would like to make suggestions, please feel free todo so.
David Latchman
Document Changes
05-11-2009 1. Added diagrams to GR0177 test questions 1-25
2. Revised solutions to GR0177 questions 1-25
04-15-2009 First Version
DRAFT
ii
David S. Latchman ©2009
DRAFTContents
Preface i
Classical Mechanics xv
0.1 Kinematics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xv
0.2 Newton’s Laws . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvi
0.3 Work & Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
0.4 Oscillatory Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xviii
0.5 Rotational Motion about a Fixed Axis . . . . . . . . . . . . . . . . . . . . xxii
0.6 Dynamics of Systems of Particles . . . . . . . . . . . . . . . . . . . . . . . xxiv
0.7 Central Forces and Celestial Mechanics . . . . . . . . . . . . . . . . . . . xxiv
0.8 Three Dimensional Particle Dynamics . . . . . . . . . . . . . . . . . . . . xxvi
0.9 Fluid Dynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxvi
0.10 Non-inertial Reference Frames . . . . . . . . . . . . . . . . . . . . . . . . xxvii
0.11 Hamiltonian and Lagrangian Formalism . . . . . . . . . . . . . . . . . . . xxvii
Electromagnetism xxix
0.12 Electrostatics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxix
0.13 Currents and DC Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiv
0.14 Magnetic Fields in Free Space . . . . . . . . . . . . . . . . . . . . . . . . . xxxiv
0.15 Lorentz Force . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiv
0.16 Induction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiv
0.17 Maxwell’s Equations and their Applications . . . . . . . . . . . . . . . . . xxxiv
0.18 Electromagnetic Waves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiv
DRAFT
iv Contents0.19 AC Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxiv
0.20 Magnetic and Electric Fields in Matter . . . . . . . . . . . . . . . . . . . . xxxiv
0.21 Capacitance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxv
0.22 Energy in a Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxv
0.23 Energy in an Electric Field . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxv
0.24 Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxv
0.25 Current Destiny . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxv
0.26 Current Density of Moving Charges . . . . . . . . . . . . . . . . . . . . . xxxv
0.27 Resistance and Ohm’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . xxxv
0.28 Resistivity and Conductivity . . . . . . . . . . . . . . . . . . . . . . . . . . xxxvi
0.29 Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxvi
0.30 Kirchoff’s Loop Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxvi
0.31 Kirchoff’s Junction Rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxvi
0.32 RC Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxvi
0.33 Maxwell’s Equations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxvi
0.34 Speed of Propagation of a Light Wave . . . . . . . . . . . . . . . . . . . . xxxvii
0.35 Relationship between E and B Fields . . . . . . . . . . . . . . . . . . . . . xxxvii
0.36 Energy Density of an EM wave . . . . . . . . . . . . . . . . . . . . . . . . xxxviii
0.37 Poynting’s Vector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxviii
Optics & Wave Phonomena xxxix
0.38 Wave Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxix
0.39 Superposition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxix
0.40 Interference . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxix
0.41 Diffraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxix
0.42 Geometrical Optics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxix
0.43 Polarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxxix
0.44 Doppler Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xl
0.45 Snell’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xl
Thermodynamics & Statistical Mechanics xli
0.46 Laws of Thermodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . xli
0.47 Thermodynamic Processes . . . . . . . . . . . . . . . . . . . . . . . . . . . xli
David S. Latchman ©2009
DRAFT
Contents v0.48 Equations of State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xli
0.49 Ideal Gases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xli
0.50 Kinetic Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xli
0.51 Ensembles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xli
0.52 Statistical Concepts and Calculation of Thermodynamic Properties . . . xlii
0.53 Thermal Expansion & Heat Transfer . . . . . . . . . . . . . . . . . . . . . xlii
0.54 Heat Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xlii
0.55 Specific Heat Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xlii
0.56 Heat and Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xlii
0.57 First Law of Thermodynamics . . . . . . . . . . . . . . . . . . . . . . . . . xlii
0.58 Work done by Ideal Gas at Constant Temperature . . . . . . . . . . . . . xliii
0.59 Heat Conduction Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . xliii
0.60 Ideal Gas Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xliv
0.61 Stefan-Boltzmann’s FormulaStefan-Boltzmann’s Equation . . . . . . . . xliv
0.62 RMS Speed of an Ideal Gas . . . . . . . . . . . . . . . . . . . . . . . . . . xliv
0.63 Translational Kinetic Energy . . . . . . . . . . . . . . . . . . . . . . . . . . xliv
0.64 Internal Energy of a Monatomic gas . . . . . . . . . . . . . . . . . . . . . xliv
0.65 Molar Specific Heat at Constant Volume . . . . . . . . . . . . . . . . . . . xlv
0.66 Molar Specific Heat at Constant Pressure . . . . . . . . . . . . . . . . . . xlv
0.67 Equipartition of Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . xlv
0.68 Adiabatic Expansion of an Ideal Gas . . . . . . . . . . . . . . . . . . . . . xlvii
0.69 Second Law of Thermodynamics . . . . . . . . . . . . . . . . . . . . . . . xlvii
Quantum Mechanics xlix
0.70 Fundamental Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xlix
0.71 Schrodinger Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xlix
0.72 Spin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . liv
0.73 Angular Momentum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . liv
0.74 Wave Funtion Symmetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . liv
0.75 Elementary Perturbation Theory . . . . . . . . . . . . . . . . . . . . . . . liv
Atomic Physics lv
0.76 Properties of Electrons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lv
©2009 David S. Latchman
DRAFT
vi Contents0.77 Bohr Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lv
0.78 Energy Quantization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lvi
0.79 Atomic Structure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lvi
0.80 Atomic Spectra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lvi
0.81 Selection Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lvii
0.82 Black Body Radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lvii
0.83 X-Rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lviii
0.84 Atoms in Electric and Magnetic Fields . . . . . . . . . . . . . . . . . . . . lix
Special Relativity lxiii
0.85 Introductory Concepts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxiii
0.86 Time Dilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxiii
0.87 Length Contraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxiii
0.88 Simultaneity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxiii
0.89 Energy and Momentum . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxiv
0.90 Four-Vectors and Lorentz Transformation . . . . . . . . . . . . . . . . . . lxv
0.91 Velocity Addition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxvi
0.92 Relativistic Doppler Formula . . . . . . . . . . . . . . . . . . . . . . . . . lxvi
0.93 Lorentz Transformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxvi
0.94 Space-Time Interval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxvii
Laboratory Methods lxix
0.95 Data and Error Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxix
0.96 Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxi
0.97 Radiation Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxi
0.98 Counting Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxi
0.99 Interaction of Charged Particles with Matter . . . . . . . . . . . . . . . . lxxii
0.100Lasers and Optical Interferometers . . . . . . . . . . . . . . . . . . . . . . lxxii
0.101Dimensional Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxii
0.102Fundamental Applications of Probability and Statistics . . . . . . . . . . lxxii
GR8677 Exam Solutions lxxiii
0.103Motion of Rock under Drag Force . . . . . . . . . . . . . . . . . . . . . . . lxxiii
David S. Latchman ©2009
DRAFT
Contents vii0.104Satellite Orbits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxiv
0.105Speed of Light in a Dielectric Medium . . . . . . . . . . . . . . . . . . . . lxxiv
0.106Wave Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxiv
0.107Inelastic Collision and Putty Spheres . . . . . . . . . . . . . . . . . . . . . lxxv
0.108Motion of a Particle along a Track . . . . . . . . . . . . . . . . . . . . . . . lxxvi
0.109Resolving Force Components . . . . . . . . . . . . . . . . . . . . . . . . . lxxvi
0.110Nail being driven into a block of wood . . . . . . . . . . . . . . . . . . . . lxxvii
0.111Current Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxvii
0.112Charge inside an Isolated Sphere . . . . . . . . . . . . . . . . . . . . . . . lxxviii
0.113Vector Identities and Maxwell’s Laws . . . . . . . . . . . . . . . . . . . . lxxix
0.114Doppler Equation (Non-Relativistic) . . . . . . . . . . . . . . . . . . . . . lxxix
0.115Vibrating Interference Pattern . . . . . . . . . . . . . . . . . . . . . . . . . lxxix
0.116Specific Heat at Constant Pressure and Volume . . . . . . . . . . . . . . . lxxix
0.117Helium atoms in a box . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxx
0.118The Muon . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxi
0.119Radioactive Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxi
0.120Schrodinger’s Equation . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxii
0.121Energy Levels of Bohr’s Hydrogen Atom . . . . . . . . . . . . . . . . . . lxxxii
0.122Relativistic Energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxiii
0.123Space-Time Interval . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxiii
0.124Lorentz Transformation of the EM field . . . . . . . . . . . . . . . . . . . lxxxiv
0.125Conductivity of a Metal and Semi-Conductor . . . . . . . . . . . . . . . . lxxxiv
0.126Charging a Battery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxv
0.127Lorentz Force on a Charged Particle . . . . . . . . . . . . . . . . . . . . . lxxxv
0.128K-Series X-Rays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxv
0.129Electrons and Spin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxvi
0.130Normalizing a wavefunction . . . . . . . . . . . . . . . . . . . . . . . . . lxxxvii
0.131Right Hand Rule . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxviii
0.132Electron Configuration of a Potassium atom . . . . . . . . . . . . . . . . . lxxxviii
0.133Photoelectric Effect I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxix
0.134Photoelectric Effect II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxix
0.135Photoelectric Effect III . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxix
©2009 David S. Latchman
DRAFT
viii Contents0.136Potential Energy of a Body . . . . . . . . . . . . . . . . . . . . . . . . . . . lxxxix
0.137Hamiltonian of a Body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xc
0.138Principle of Least Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . xc
0.139Tension in a Conical Pendulum . . . . . . . . . . . . . . . . . . . . . . . . xc
0.140Diode OR-gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xci
0.141Gain of an Amplifier vs. Angular Frequency . . . . . . . . . . . . . . . . xci
0.142Counting Statistics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xci
0.143Binding Energy per Nucleon . . . . . . . . . . . . . . . . . . . . . . . . . . xcii
0.144Scattering Cross Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . xcii
0.145Coupled Oscillators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xcii
0.146Collision with a Rod . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xciv
0.147Compton Wavelength . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xciv
0.148Stefan-Boltzmann’s Equation . . . . . . . . . . . . . . . . . . . . . . . . . xciv
0.149Franck-Hertz Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . xcv
0.150Selection Rules for Electronic Transitions . . . . . . . . . . . . . . . . . . xcv
0.151The Hamilton Operator . . . . . . . . . . . . . . . . . . . . . . . . . . . . xcv
0.152Hall Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xcvi
0.153Debye and Einstein Theories to Specific Heat . . . . . . . . . . . . . . . . xcvii
0.154Potential inside a Hollow Cube . . . . . . . . . . . . . . . . . . . . . . . . xcvii
0.155EM Radiation from Oscillating Charges . . . . . . . . . . . . . . . . . . . xcviii
0.156Polarization Charge Density . . . . . . . . . . . . . . . . . . . . . . . . . . xcviii
0.157Kinetic Energy of Electrons in Metals . . . . . . . . . . . . . . . . . . . . . xcviii
0.158Expectation or Mean Value . . . . . . . . . . . . . . . . . . . . . . . . . . . xcix
0.159Eigenfuction of Wavefunction . . . . . . . . . . . . . . . . . . . . . . . . . xcix
0.160Holograms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . c
0.161Group Velocity of a Wave . . . . . . . . . . . . . . . . . . . . . . . . . . . ci
0.162Potential Energy and Simple Harmonic Motion . . . . . . . . . . . . . . . ci
0.163Rocket Equation I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cii
0.164Rocket Equation II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cii
0.165Surface Charge Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cii
0.166Maximum Power Theorem . . . . . . . . . . . . . . . . . . . . . . . . . . . ciii
0.167Magnetic Field far away from a Current carrying Loop . . . . . . . . . . ciii
David S. Latchman ©2009
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Contents ix0.168Maxwell’s Relations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . civ
0.169Partition Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cv
0.170Particle moving at Light Speed . . . . . . . . . . . . . . . . . . . . . . . . cv
0.171Car and Garage I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cv
0.172Car and Garage II . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cvi
0.173Car and Garage III . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cvi
0.174Refrective Index of Rock Salt and X-rays . . . . . . . . . . . . . . . . . . . cvi
0.175Thin Flim Non-Reflective Coatings . . . . . . . . . . . . . . . . . . . . . . cvii
0.176Law of Malus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cvii
0.177Geosynchronous Satellite Orbit . . . . . . . . . . . . . . . . . . . . . . . . cviii
0.178Hoop Rolling down and Inclined Plane . . . . . . . . . . . . . . . . . . . cviii
0.179Simple Harmonic Motion . . . . . . . . . . . . . . . . . . . . . . . . . . . cix
0.180Total Energy between Two Charges . . . . . . . . . . . . . . . . . . . . . . cx
0.181Maxwell’s Equations and Magnetic Monopoles . . . . . . . . . . . . . . . cx
0.182Gauss’ Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxi
0.183Biot-Savart Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxii
0.184Zeeman Effect and the emission spectrum of atomic gases . . . . . . . . cxii
0.185Spectral Lines in High Density and Low Density Gases . . . . . . . . . . cxiii
0.186Term Symbols & Spectroscopic Notation . . . . . . . . . . . . . . . . . . . cxiii
0.187Photon Interaction Cross Sections for Pb . . . . . . . . . . . . . . . . . . . cxiv
0.188The Ice Pail Experiment . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxiv
0.189Equipartition of Energy and Diatomic Molecules . . . . . . . . . . . . . . cxiv
0.190Fermion and Boson Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . cxv
0.191Wavefunction of Two Identical Particles . . . . . . . . . . . . . . . . . . . cxv
0.192Energy Eigenstates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxvi
0.193Bragg’s Law . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxvii
0.194Selection Rules for Electronic Transitions . . . . . . . . . . . . . . . . . . cxvii
0.195Moving Belt Sander on a Rough Plane . . . . . . . . . . . . . . . . . . . . cxviii
0.196RL Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxviii
0.197Carnot Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxx
0.198First Order Perturbation Theory . . . . . . . . . . . . . . . . . . . . . . . . cxxii
0.199Colliding Discs and the Conservation of Angular Momentum . . . . . . cxxii
©2009 David S. Latchman
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x Contents0.200Electrical Potential of a Long Thin Rod . . . . . . . . . . . . . . . . . . . . cxxiii
0.201Ground State of a Positronium Atom . . . . . . . . . . . . . . . . . . . . . cxxiv
0.202The Pinhole Camera . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxxiv
Constants & Important Equations cxxvii
.1 Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxxvii
.2 Vector Identities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxxvii
.3 Commutators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxxviii
.4 Linear Algebra . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxxix
David S. Latchman ©2009
DRAFTList of Tables
0.67.1Table of Molar Specific Heats . . . . . . . . . . . . . . . . . . . . . . . . . xlvi
0.140.1Truth Table for OR-gate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xci
0.189.1Specific Heat, cv for a diatomic molecule . . . . . . . . . . . . . . . . . . . cxiv
.1.1 Something . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cxxvii
DRAFT
xii List of Tables
David S. Latchman ©2009
DRAFTList of Figures
DRAFT
xiv List of Figures
David S. Latchman ©2009
DRAFTClassical Mechanics
0.1 Kinematics
0.1.1 Linear Motion
Average Velocity
v =∆x∆t
=x2 − x1
t2 − t1(0.1.1)
Instantaneous Velocity
v = lim∆t→0
∆x∆t
=dxdt
= v(t) (0.1.2)
Kinematic Equations of Motion
The basic kinematic equations of motion under constant acceleration, a, are
v = v0 + at (0.1.3)
v2 = v20 + 2a (x − x0) (0.1.4)
x − x0 = v0t +12
at2 (0.1.5)
x − x0 =12
(v + v0) t (0.1.6)
0.1.2 Circular Motion
In the case of Uniform Circular Motion, for a particle to move in a circular path, aradial acceleration must be applied. This acceleration is known as the CentripetalAcceleration
DRAFT
xvi Classical MechanicsCentripetal Acceleration
a =v2
r(0.1.7)
Angular Velocity
ω =vr
(0.1.8)
We can write eq. (0.1.7) in terms of ω
a = ω2r (0.1.9)
Rotational Equations of Motion
The equations of motion under a constant angular acceleration, α, are
ω = ω0 + αt (0.1.10)
θ =ω + ω0
2t (0.1.11)
θ = ω0t +12αt2 (0.1.12)
ω2 = ω20 + 2αθ (0.1.13)
0.2 Newton’s Laws
0.2.1 Newton’s Laws of Motion
First Law A body continues in its state of rest or of uniform motion unless acted uponby an external unbalanced force.
Second Law The net force on a body is proportional to its rate of change of momentum.
F =dpdt
= ma (0.2.1)
Third Law When a particle A exerts a force on another particle B, B simultaneouslyexerts a force on A with the same magnitude in the opposite direction.
FAB = −FBA (0.2.2)
0.2.2 Momentum
p = mv (0.2.3)
David S. Latchman ©2009
DRAFT
Work & Energy xvii0.2.3 Impulse
∆p = J =w
Fdt = Favgdt (0.2.4)
0.3 Work & Energy
0.3.1 Kinetic Energy
K ≡12
mv2 (0.3.1)
0.3.2 The Work-Energy Theorem
The net Work done is given byWnet = K f − Ki (0.3.2)
0.3.3 Work done under a constant Force
The work done by a force can be expressed as
W = F∆x (0.3.3)
In three dimensions, this becomes
W = F · ∆r = F∆r cosθ (0.3.4)
For a non-constant force, we have
W =
x fw
xi
F(x)dx (0.3.5)
0.3.4 Potential Energy
The Potential Energy is
F(x) = −dU(x)
dx(0.3.6)
for conservative forces, the potential energy is
U(x) = U0 −
xw
x0
F(x′)dx′ (0.3.7)
©2009 David S. Latchman
DRAFT
xviii Classical Mechanics0.3.5 Hooke’s Law
F = −kx (0.3.8)
where k is the spring constant.
0.3.6 Potential Energy of a Spring
U(x) =12
kx2 (0.3.9)
0.4 Oscillatory Motion
0.4.1 Equation for Simple Harmonic Motion
x(t) = A sin (ωt + δ) (0.4.1)
where the Amplitude, A, measures the displacement from equilibrium, the phase, δ, isthe angle by which the motion is shifted from equilibrium at t = 0.
0.4.2 Period of Simple Harmonic Motion
T =2πω
(0.4.2)
0.4.3 Total Energy of an Oscillating System
Given thatx = A sin (ωt + δ) (0.4.3)
and that the Total Energy of a System is
E = KE + PE (0.4.4)
The Kinetic Energy is
KE =12
mv2
=12
mdxdt
=12
mA2ω2 cos2 (ωt + δ) (0.4.5)
David S. Latchman ©2009
DRAFT
Oscillatory Motion xixThe Potential Energy is
U =12
kx2
=12
kA2 sin2 (ωt + δ) (0.4.6)
Adding eq. (0.4.5) and eq. (0.4.6) gives
E =12
kA2 (0.4.7)
0.4.4 Damped Harmonic Motion
Fd = −bv = −bdxdt
(0.4.8)
where b is the damping coefficient. The equation of motion for a damped oscillatingsystem becomes
− kx − bdxdt
= md2xdt2 (0.4.9)
Solving eq. (0.4.9) govesx = Ae−αt sin (ω′t + δ) (0.4.10)
We find that
α =b
2m(0.4.11)
ω′ =
√km−
b2
4m2
=
√ω2
0 −b2
4m2
=√ω2
0 − α2 (0.4.12)
0.4.5 Small Oscillations
The Energy of a system is
E = K + V(x) =12
mv(x)2 + V(x) (0.4.13)
We can solve for v(x),
v(x) =
√2m
(E − V(x)) (0.4.14)
where E ≥ V(x) Let the particle move in the potential valley, x1 ≤ x ≤ x2, the potentialcan be approximated by the Taylor Expansion
V(x) = V(xe) + (x − xe)[dV(x)
dx
]x=xe
+12
(x − xe)2
[d2V(x)
dx2
]x=xe
+ · · · (0.4.15)
©2009 David S. Latchman
DRAFT
xx Classical MechanicsAt the points of inflection, the derivative dV/dx is zero and d2V/dx2 is positive. Thismeans that the potential energy for small oscillations becomes
V(x) u V(xe) +12
k(x − xe)2 (0.4.16)
where
k ≡[d2V(x)
dx2
]x=xe
≥ 0 (0.4.17)
As V(xe) is constant, it has no consequences to physical motion and can be dropped.We see that eq. (0.4.16) is that of simple harmonic motion.
0.4.6 Coupled Harmonic Oscillators
Consider the case of a simple pendulum of length, `, and the mass of the bob is m1.For small displacements, the equation of motion is
θ + ω0θ = 0 (0.4.18)
We can express this in cartesian coordinates, x and y, where
x = ` cosθ ≈ ` (0.4.19)y = ` sinθ ≈ `θ (0.4.20)
eq. (0.4.18) becomesy + ω0y = 0 (0.4.21)
This is the equivalent to the mass-spring system where the spring constant is
k = mω20 =
mg`
(0.4.22)
This allows us to to create an equivalent three spring system to our coupled pendulumsystem. The equations of motion can be derived from the Lagrangian, where
L = T − V
=12
my21 +
12
my22 −
(12
ky21 +
12κ(y2 − y1
)2+
12
ky22
)=
12
m(y1
2 + y22)−
12
(k(y2
1 + y22
)+ κ
(y2 − y1
)2)
(0.4.23)
We can find the equations of motion of our system
ddt
(∂L∂yn
)=∂L∂yn
(0.4.24)
1Add figure with coupled pendulum-spring system
David S. Latchman ©2009
DRAFT
Oscillatory Motion xxiThe equations of motion are
my1 = −ky1 + κ(y2 − y1
)(0.4.25)
my2 = −ky2 + κ(y2 − y1
)(0.4.26)
We assume solutions for the equations of motion to be of the form
y1 = cos(ωt + δ1) y2 = B cos(ωt + δ2)y1 = −ωy1 y2 = −ωy2
(0.4.27)
Substituting the values for y1 and y2 into the equations of motion yields(k + κ −mω2
)y1 − κy2 = 0 (0.4.28)
−κy1 +(k + κ −mω2
)y2 = 0 (0.4.29)
We can get solutions from solving the determinant of the matrix∣∣∣∣∣(k + κ −mω2)−κ
−κ(k + κ −mω2)∣∣∣∣∣ = 0 (0.4.30)
Solving the determinant gives(mω2
)2− 2mω2 (k + κ) +
(k2 + 2kκ
)= 0 (0.4.31)
This yields
ω2 =
km
=g`
k + 2κm
=g`
+2κm
(0.4.32)
We can now determine exactly how the masses move with each mode by substitutingω2 into the equations of motion. Where
ω2 =km
We see that
k + κ −mω2 = κ (0.4.33)
Substituting this into the equation of motion yields
y1 = y2 (0.4.34)
We see that the masses move in phase with each other. You will also noticethe absense of the spring constant term, κ, for the connecting spring. As themasses are moving in step, the spring isn’t stretching or compressing and henceits absence in our result.
ω2 =k + κ
mWe see that
k + κ −mω2 = −κ (0.4.35)
Substituting this into the equation of motion yields
y1 = −y2 (0.4.36)
Here the masses move out of phase with each other. In this case we see thepresence of the spring constant, κ, which is expected as the spring playes a role.It is being stretched and compressed as our masses oscillate.
©2009 David S. Latchman
DRAFT
xxii Classical Mechanics0.4.7 Doppler Effect
The Doppler Effect is the shift in frequency and wavelength of waves that results froma source moving with respect to the medium, a receiver moving with respect to themedium or a moving medium.
Moving Source If a source is moving towards an observer, then in one period, τ0, itmoves a distance of vsτ0 = vs/ f0. The wavelength is decreased by
λ′ = λ −vs
f0−
v − vs
f0(0.4.37)
The frequency change is
f ′ =vλ′
= f0
( vv − vs
)(0.4.38)
Moving Observer As the observer moves, he will measure the same wavelength, λ, asif at rest but will see the wave crests pass by more quickly. The observer measuresa modified wave speed.
v′ = v + |vr| (0.4.39)
The modified frequency becomes
f ′ =v′
λ= f0
(1 +
vr
v
)(0.4.40)
Moving Source and Moving Observer We can combine the above two equations
λ′ =v − vs
f0(0.4.41)
v′ = v − vr (0.4.42)
To give a modified frequency of
f ′ =v′
λ′=
(v − vr
v − vs
)f0 (0.4.43)
0.5 Rotational Motion about a Fixed Axis
0.5.1 Moment of Inertia
I =
∫R2dm (0.5.1)
0.5.2 Rotational Kinetic Energy
K =12
Iω2 (0.5.2)
David S. Latchman ©2009
DRAFT
Rotational Motion about a Fixed Axis xxiii0.5.3 Parallel Axis Theorem
I = Icm + Md2 (0.5.3)
0.5.4 Torque
τ = r × F (0.5.4)τ = Iα (0.5.5)
where α is the angular acceleration.
0.5.5 Angular Momentum
L = Iω (0.5.6)
we can find the Torque
τ =dLdt
(0.5.7)
0.5.6 Kinetic Energy in Rolling
With respect to the point of contact, the motion of the wheel is a rotation about thepoint of contact. Thus
K = Krot =12
Icontactω2 (0.5.8)
Icontact can be found from the Parallel Axis Theorem.
Icontact = Icm + MR2 (0.5.9)
Substitute eq. (0.5.8) and we have
K =12
(Icm + MR2
)ω2
=12
Icmω2 +
12
mv2 (0.5.10)
The kinetic energy of an object rolling without slipping is the sum of hte kinetic energyof rotation about its center of mass and the kinetic energy of the linear motion of theobject.
©2009 David S. Latchman
DRAFT
xxiv Classical Mechanics0.6 Dynamics of Systems of Particles
0.6.1 Center of Mass of a System of Particles
Position Vector of a System of Particles
R =m1r1 + m2r2 + m3r3 + · · · + mNrN
M(0.6.1)
Velocity Vector of a System of Particles
V =dRdt
=m1v1 + m2v2 + m3v3 + · · · + mNvN
M(0.6.2)
Acceleration Vector of a System of Particles
A =dVdt
=m1a1 + m2a2 + m3a3 + · · · + mNaN
M(0.6.3)
0.7 Central Forces and Celestial Mechanics
0.7.1 Newton’s Law of Universal Gravitation
F = −(GMm
r2
)r (0.7.1)
0.7.2 Potential Energy of a Gravitational Force
U(r) = −GMm
r(0.7.2)
0.7.3 Escape Speed and Orbits
The energy of an orbiting body is
E = T + U
=12
mv2−
GMmr
(0.7.3)
David S. Latchman ©2009
DRAFT
Central Forces and Celestial Mechanics xxvThe escape speed becomes
E =12
mv2esc −
GMmRE
= 0 (0.7.4)
Solving for vesc we find
vesc =
√2GM
Re(0.7.5)
0.7.4 Kepler’s Laws
First Law The orbit of every planet is an ellipse with the sun at a focus.
Second Law A line joining a planet and the sun sweeps out equal areas during equalintervals of time.
Third Law The square of the orbital period of a planet is directly proportional to thecube of the semi-major axis of its orbit.
T2
R3 = C (0.7.6)
where C is a constant whose value is the same for all planets.
0.7.5 Types of Orbits
The Energy of an Orbiting Body is defined in eq. (0.7.3), we can classify orbits by theireccentricities.
Circular Orbit A circular orbit occurs when there is an eccentricity of 0 and the orbitalenergy is less than 0. Thus
12
v2−
GMr
= E < 0 (0.7.7)
The Orbital Velocity is
v =
√GM
r(0.7.8)
Elliptic Orbit An elliptic orbit occurs when the eccentricity is between 0 and 1 but thespecific energy is negative, so the object remains bound.
v =
√GM
(2r−
1a
)(0.7.9)
where a is the semi-major axis
©2009 David S. Latchman
DRAFT
xxvi Classical MechanicsParabolic Orbit A Parabolic Orbit occurs when the eccentricity is equal to 1 and the
orbital velocity is the escape velocity. This orbit is not bounded. Thus
12
v2−
GMr
= E = 0 (0.7.10)
The Orbital Velocity is
v = vesc =
√2GM
r(0.7.11)
Hyperbolic Orbit In the Hyperbolic Orbit, the eccentricity is greater than 1 with anorbital velocity in excess of the escape velocity. This orbit is also not bounded.
v∞ =
√GM
a(0.7.12)
0.7.6 Derivation of Vis-viva Equation
The total energy of a satellite is
E =12
mv2−
GMmr
(0.7.13)
For an elliptical or circular orbit, the specific energy is
E = −GMm
2a(0.7.14)
Equating we get
v2 = GM(2
r−
1a
)(0.7.15)
0.8 Three Dimensional Particle Dynamics
0.9 Fluid Dynamics
When an object is fully or partially immersed, the buoyant force is equal to the weightof fluid displaced.
0.9.1 Equation of Continuity
ρ1v1A1 = ρ2v2A2 (0.9.1)
David S. Latchman ©2009
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Non-inertial Reference Frames xxvii0.9.2 Bernoulli’s Equation
P +12ρv2 + ρgh = a constant (0.9.2)
0.10 Non-inertial Reference Frames
0.11 Hamiltonian and Lagrangian Formalism
0.11.1 Lagrange’s Function (L)
L = T − V (0.11.1)
where T is the Kinetic Energy and V is the Potential Energy in terms of GeneralizedCoordinates.
0.11.2 Equations of Motion(Euler-Lagrange Equation)
∂L∂q
=ddt
(∂L∂q
)(0.11.2)
0.11.3 Hamiltonian
H = T + V= pq − L(q, q) (0.11.3)
where
∂H∂p
= q (0.11.4)
∂H∂q
= −∂L∂x
= −p (0.11.5)
©2009 David S. Latchman
DRAFT
xxviii Classical Mechanics
David S. Latchman ©2009
DRAFTElectromagnetism
0.12 Electrostatics
0.12.1 Coulomb’s Law
The force between two charged particles, q1 and q2 is defined by Coulomb’s Law.
F12 =1
4πε0
(q1q2
r212
)r12 (0.12.1)
where ε0 is the permitivitty of free space, where
ε0 = 8.85 × 10−12C2N.m2 (0.12.2)
0.12.2 Electric Field of a point charge
The electric field is defined by mesuring the magnitide and direction of an electricforce, F, acting on a test charge, q0.
E ≡Fq0
(0.12.3)
The Electric Field of a point charge, q is
E =1
4πε0
qr2 r (0.12.4)
In the case of multiple point charges, qi, the electric field becomes
E(r) =1
4πε0
n∑i=1
qi
r2i
ri (0.12.5)
Electric Fields and Continuous Charge Distributions
If a source is distributed continuously along a region of space, eq. (0.12.5) becomes
E(r) =1
4πε0
∫1r2 rdq (0.12.6)
DRAFT
xxx ElectromagnetismIf the charge was distributed along a line with linear charge density, λ,
λ =dqdx
(0.12.7)
The Electric Field of a line charge becomes
E(r) =1
4πε0
∫line
λr2 rdx (0.12.8)
In the case where the charge is distributed along a surface, the surface charge densityis, σ
σ =QA
=dqdA
(0.12.9)
The electric field along the surface becomes
E(r) =1
4πε0
∫Surface
σr2 rdA (0.12.10)
In the case where the charge is distributed throughout a volume, V, the volume chargedensity is
ρ =QV
=dqdV
(0.12.11)
The Electric Field is
E(r) =1
4πε0
∫Volume
ρ
r2 rdV (0.12.12)
0.12.3 Gauss’ Law
The electric field through a surface is
Φ =
∮surface S
dΦ =
∮surface S
E · dA (0.12.13)
The electric flux through a closed surface encloses a net charge.∮E · dA =
Qε0
(0.12.14)
where Q is the charge enclosed by our surface.
David S. Latchman ©2009
DRAFT
Electrostatics xxxi0.12.4 Equivalence of Coulomb’s Law and Gauss’ Law
The total flux through a sphere is∮E · dA = E(4πr2) =
qε0
(0.12.15)
From the above, we see that the electric field is
E =q
4πε0r2 (0.12.16)
0.12.5 Electric Field due to a line of charge
Consider an infinite rod of constant charge density, λ. The flux through a Gaussiancylinder enclosing the line of charge is
Φ =
∫top surface
E · dA +
∫bottom surface
E · dA +
∫side surface
E · dA (0.12.17)
At the top and bottom surfaces, the electric field is perpendicular to the area vector, sofor the top and bottom surfaces,
E · dA = 0 (0.12.18)
At the side, the electric field is parallel to the area vector, thus
E · dA = EdA (0.12.19)
Thus the flux becomes,
Φ =
∫side sirface
E · dA = E∫
dA (0.12.20)
The area in this case is the surface area of the side of the cylinder, 2πrh.
Φ = 2πrhE (0.12.21)
Applying Gauss’ Law, we see that Φ = q/ε0. The electric field becomes
E =λ
2πε0r(0.12.22)
0.12.6 Electric Field in a Solid Non-Conducting Sphere
Within our non-conducting sphere or radius, R, we will assume that the total charge,Q is evenly distributed throughout the sphere’s volume. So the charge density of oursphere is
ρ =QV
=Q
43πR3
(0.12.23)
©2009 David S. Latchman
DRAFT
xxxii ElectromagnetismThe Electric Field due to a charge Q is
E =Q
4πε0r2 (0.12.24)
As the charge is evenly distributed throughout the sphere’s volume we can say thatthe charge density is
dq = ρdV (0.12.25)
where dV = 4πr2dr. We can use this to determine the field inside the sphere bysumming the effect of infinitesimally thin spherical shells
E =
∫ E
0dE =
∫ r
0
dq4πεr2
=ρ
ε0
∫ r
0dr
=Qr
43πε0R3
(0.12.26)
0.12.7 Electric Potential Energy
U(r) =1
4πε0qq0r (0.12.27)
0.12.8 Electric Potential of a Point Charge
The electrical potential is the potential energy per unit charge that is associated with astatic electrical field. It can be expressed thus
U(r) = qV(r) (0.12.28)
And we can see that
V(r) =1
4πε0
qr
(0.12.29)
A more proper definition that includes the electric field, E would be
V(r) = −
∫C
E · d` (0.12.30)
where C is any path, starting at a chosen point of zero potential to our desired point.
The difference between two potentials can be expressed such
V(b) − V(a) = −
∫ b
E · d` +
∫ a
E · d`
= −
∫ b
aE · d` (0.12.31)
David S. Latchman ©2009
DRAFT
Electrostatics xxxiiiThis can be further expressed
V(b) − V(a) =
∫ b
a(∇V) · d` (0.12.32)
And we can show thatE = −∇V (0.12.33)
0.12.9 Electric Potential due to a line charge along axis
Let us consider a rod of length, `, with linear charge density, λ. The Electrical Potentialdue to a continuous distribution is
V =
∫dV =
14πε0
∫dqr
(0.12.34)
The charge density isdq = λdx (0.12.35)
Substituting this into the above equation, we get the electrical potential at some distancex along the rod’s axis, with the origin at the start of the rod.
dV =1
4πε0
dqx
=1
4πε0
λdxx
(0.12.36)
This becomesV =
λ4πε0
ln[x2
x1
](0.12.37)
where x1 and x2 are the distances from O, the end of the rod.
Now consider that we are some distance, y, from the axis of the rod of length, `. Weagain look at eq. (0.12.34), where r is the distance of the point P from the rod’s axis.
V =1
4πε0
∫dqr
=1
4πε0
∫ `
0
λdx(x2 + y2
) 12
=λ
4πε0ln
[x +
(x2 + y2
) 12]`
0
=λ
4πε0ln
[` +
(`2 + y2
) 12]− ln y
=λ
4πε0ln
` +(`2 + y2) 1
2
d
(0.12.38)
©2009 David S. Latchman
DRAFT
xxxiv Electromagnetism0.13 Currents and DC Circuits
2
0.14 Magnetic Fields in Free Space
3
0.15 Lorentz Force
4
0.16 Induction
5
0.17 Maxwell’s Equations and their Applications
6
0.18 Electromagnetic Waves
7
0.19 AC Circuits
8
0.20 Magnetic and Electric Fields in Matter
9
David S. Latchman ©2009
DRAFT
Capacitance xxxv0.21 Capacitance
Q = CV (0.21.1)
0.22 Energy in a Capacitor
U =Q2
2C
=CV2
2
=QV
2(0.22.1)
0.23 Energy in an Electric Field
u ≡U
volume=ε0E2
2(0.23.1)
0.24 Current
I ≡dQdt
(0.24.1)
0.25 Current Destiny
I =
∫A
J · dA (0.25.1)
0.26 Current Density of Moving Charges
J =IA
= neqvd (0.26.1)
0.27 Resistance and Ohm’s Law
R ≡VI
(0.27.1)
©2009 David S. Latchman
DRAFT
xxxvi Electromagnetism0.28 Resistivity and Conductivity
R = ρLA
(0.28.1)
E = ρJ (0.28.2)
J = σE (0.28.3)
0.29 Power
P = VI (0.29.1)
0.30 Kirchoff’s Loop Rules
Write Here
0.31 Kirchoff’s Junction Rule
Write Here
0.32 RC Circuits
E − IR −QC
= 0 (0.32.1)
0.33 Maxwell’s Equations
0.33.1 Integral Form
Gauss’ Law for Electric Fieldsw
closed surface
E · dA =Qε0
(0.33.1)
David S. Latchman ©2009
DRAFT
Speed of Propagation of a Light Wave xxxviiGauss’ Law for Magnetic Fields
w
closed surface
B · dA = 0 (0.33.2)
Ampere’s Lawz
B · ds = µ0I + µ0ε0ddt
w
surface
E · dA (0.33.3)
Faraday’s Lawz
E · ds = −ddt
w
surface
B · dA (0.33.4)
0.33.2 Differential Form
Gauss’ Law for Electric Fields∇ · E =
ρ
ε0(0.33.5)
Gauss’ Law for Magnetism∇ · B = 0 (0.33.6)
Ampere’s Law
∇ × B = µ0J + µ0ε0∂E∂t
(0.33.7)
Faraday’s Law
∇ · E = −∂B∂t
(0.33.8)
0.34 Speed of Propagation of a Light Wave
c =1
√µ0ε0
(0.34.1)
In a material with dielectric constant, κ,
c√κ =
cn
(0.34.2)
where n is the refractive index.
0.35 Relationship between E and B Fields
E = cB (0.35.1)E · B = 0 (0.35.2)
©2009 David S. Latchman
DRAFT
xxxviii Electromagnetism0.36 Energy Density of an EM wave
u =12
(B2
µ0+ ε0E2
)(0.36.1)
0.37 Poynting’s Vector
S =1µ0
E × B (0.37.1)
David S. Latchman ©2009
DRAFTOptics & Wave Phonomena
0.38 Wave Properties
1
0.39 Superposition
2
0.40 Interference
3
0.41 Diffraction
4
0.42 Geometrical Optics
5
0.43 Polarization
6
DRAFT
xl Optics & Wave Phonomena0.44 Doppler Effect
7
0.45 Snell’s Law
0.45.1 Snell’s Law
n1 sinθ1 = n2 sinθ2 (0.45.1)
0.45.2 Critical Angle and Snell’s Law
The critical angle, θc, for the boundary seperating two optical media is the smallestangle of incidence, in the medium of greater index, for which light is totally refelected.
From eq. (0.45.1), θ1 = 90 and θ2 = θc and n2 > n1.
n1 sin 90 = n2sinθc
sinθc =n1
n2(0.45.2)
David S. Latchman ©2009
DRAFTThermodynamics & Statistical Mechanics
0.46 Laws of Thermodynamics
1
0.47 Thermodynamic Processes
2
0.48 Equations of State
3
0.49 Ideal Gases
4
0.50 Kinetic Theory
5
0.51 Ensembles
6
DRAFT
xlii Thermodynamics & Statistical Mechanics0.52 Statistical Concepts and Calculation of Thermody-
namic Properties
7
0.53 Thermal Expansion & Heat Transfer
8
0.54 Heat Capacity
Q = C(T f − Ti
)(0.54.1)
where C is the Heat Capacity and T f and Ti are the final and initial temperaturesrespectively.
0.55 Specific Heat Capacity
Q = cm(T f − ti
)(0.55.1)
where c is the specific heat capacity and m is the mass.
0.56 Heat and Work
W =
∫ V f
Vi
PdV (0.56.1)
0.57 First Law of Thermodynamics
dEint = dQ − dW (0.57.1)
where dEint is the internal energy of the system, dQ is the Energy added to the systemand dW is the work done by the system.
David S. Latchman ©2009
DRAFT
Work done by Ideal Gas at Constant Temperature xliii0.57.1 Special Cases to the First Law of Thermodynamics
Adiabatic Process During an adiabatic process, the system is insulated such that thereis no heat transfer between the system and its environment. Thus dQ = 0, so
∆Eint = −W (0.57.2)
If work is done on the system, negative W, then there is an increase in its internalenergy. Conversely, if work is done by the system, positive W, there is a decreasein the internal energy of the system.
Constant Volume (Isochoric) Process If the volume is held constant, then the systemcan do no work, δW = 0, thus
∆Eint = Q (0.57.3)
If heat is added to the system, the temperature increases. Conversely, if heat isremoved from the system the temperature decreases.
Closed Cycle In this situation, after certain interchanges of heat and work, the systemcomes back to its initial state. So ∆Eint remains the same, thus
∆Q = ∆W (0.57.4)
The work done by the system is equal to the heat or energy put into it.
Free Expansion In this process, no work is done on or by the system. Thus ∆Q =∆W = 0,
∆Eint = 0 (0.57.5)
0.58 Work done by Ideal Gas at Constant Temperature
Starting with eq. (0.56.1), we substitute the Ideal gas Law, eq. (0.60.1), to get
W = nRT∫ V f
Vi
dVV
= nRT lnV f
Vi(0.58.1)
0.59 Heat Conduction Equation
The rate of heat transferred, H, is given by
H =Qt
= kATH − TC
L(0.59.1)
where k is the thermal conductivity.
©2009 David S. Latchman
DRAFT
xliv Thermodynamics & Statistical Mechanics0.60 Ideal Gas Law
PV = nRT (0.60.1)
where
n = Number of molesP = PressureV = VolumeT = Temperature
and R is the Universal Gas Constant, such that
R ≈ 8.314 J/mol. K
We can rewrite the Ideal gas Law to say
PV = NkT (0.60.2)
where k is the Boltzmann’s Constant, such that
k =R
NA≈ 1.381 × 10−23 J/K
0.61 Stefan-Boltzmann’s FormulaStefan-Boltzmann’s Equa-tion
P(T) = σT4 (0.61.1)
0.62 RMS Speed of an Ideal Gas
vrms =
√3RTM
(0.62.1)
0.63 Translational Kinetic Energy
K =32
kT (0.63.1)
0.64 Internal Energy of a Monatomic gas
Eint =32
nRT (0.64.1)
David S. Latchman ©2009
DRAFT
Molar Specific Heat at Constant Volume xlv0.65 Molar Specific Heat at Constant Volume
Let us define, CV such that
Q = nCV∆T (0.65.1)
Substituting into the First Law of Thermodynamics, we have
∆Eint + W = nCV∆T (0.65.2)
At constant volume, W = 0, and we get
CV =1n
∆Eint
∆T(0.65.3)
Substituting eq. (0.64.1), we get
CV =32
R = 12.5 J/mol.K (0.65.4)
0.66 Molar Specific Heat at Constant Pressure
Starting with
Q = nCp∆T (0.66.1)
and
∆Eint = Q −W⇒ nCV∆T = nCp∆T + nR∆T
∴ CV = Cp − R (0.66.2)
0.67 Equipartition of Energy
CV =
(f2
)R = 4.16 f J/mol.K (0.67.1)
where f is the number of degrees of freedom.
©2009 David S. Latchman
DRAFT
xlvi Thermodynamics & Statistical Mechanics
Degrees
ofFreedomPredicted
Molar
SpecificH
eats
Molecule
TranslationalR
otationalV
ibrationalTotal(f)
CV
CP
=C
V+
R
Monatom
ic3
00
332 R
52 RD
iatomic
32
25
52 R72 R
Polyatomic
(Linear)3
33n−
56
3R4R
Polyatomic
(Non-Linear)
33
3n−
66
3R4R
Table0.67.1:Table
ofMolar
SpecificH
eats
David S. Latchman ©2009
DRAFT
Adiabatic Expansion of an Ideal Gas xlvii0.68 Adiabatic Expansion of an Ideal Gas
PVγ = a constant (0.68.1)
where γ = CPCV
.We can also write
TVγ−1 = a constant (0.68.2)
0.69 Second Law of Thermodynamics
Something.
©2009 David S. Latchman
DRAFT
xlviii Thermodynamics & Statistical Mechanics
David S. Latchman ©2009
DRAFTQuantum Mechanics
0.70 Fundamental Concepts
1
0.71 Schrodinger Equation
Let us define Ψ to beΨ = Ae−iω(t− x
v ) (0.71.1)Simplifying in terms of Energy, E, and momentum, p, we get
Ψ = Ae−i(Et−px)~ (0.71.2)
We obtain Schrodinger’s Equation from the Hamiltonian
H = T + V (0.71.3)
To determine E and p,
∂2Ψ
∂x2 = −p2
~2 Ψ (0.71.4)
∂Ψ∂t
=iE~
Ψ (0.71.5)
and
H =p2
2m+ V (0.71.6)
This becomes
EΨ = HΨ (0.71.7)
EΨ = −~
i∂Ψ∂t
p2Ψ = −~2∂2Ψ
∂x2
The Time Dependent Schrodinger’s Equation is
i~∂Ψ∂t
= −~2
2m∂2Ψ
∂x2 + V(x)Ψ (0.71.8)
The Time Independent Schrodinger’s Equation is
EΨ = −~2
2m∂2Ψ
∂x2 + V(x)Ψ (0.71.9)
DRAFT
l Quantum Mechanics0.71.1 Infinite Square Wells
Let us consider a particle trapped in an infinite potential well of size a, such that
V(x) =
0 for 0 < x < a∞ for |x| > a,
so that a nonvanishing force acts only at ±a/2. An energy, E, is assigned to the systemsuch that the kinetic energy of the particle is E. Classically, any motion is forbiddenoutside of the well because the infinite value of V exceeds any possible choice of E.
Recalling the Schrodinger Time Independent Equation, eq. (0.71.9), we substitute V(x)and in the region (−a/2, a/2), we get
−~2
2md2ψ
dx2 = Eψ (0.71.10)
This differential is of the formd2ψ
dx2 + k2ψ = 0 (0.71.11)
where
k =
√2mE~2 (0.71.12)
We recognize that possible solutions will be of the form
cos kx and sin kx
As the particle is confined in the region 0 < x < a, we say
ψ(x) =
A cos kx + B sin kx for 0 < x < a0 for |x| > a
We have known boundary conditions for our square well.
ψ(0) = ψ(a) = 0 (0.71.13)
It shows that
⇒ A cos 0 + B sin 0 = 0∴ A = 0 (0.71.14)
We are now left with
B sin ka = 0ka = 0;π; 2π; 3π; · · ·
(0.71.15)
While mathematically, n can be zero, that would mean there would be no wave function,so we ignore this result and say
kn =nπa
for n = 1, 2, 3, · · ·
David S. Latchman ©2009
DRAFT
Schrodinger Equation liSubstituting this result into eq. (0.71.12) gives
kn =nπa
=
√2mEn
~(0.71.16)
Solving for En gives
En =n2π2~2
2ma2 (0.71.17)
We cna now solve for B by normalizing the function∫ a
0|B|2 sin2 kxdx = |A|2
a2
= 1
So |A|2 =2a
(0.71.18)
So we can write the wave function as
ψn(x) =
√2a
sin(nπx
a
)(0.71.19)
0.71.2 Harmonic Oscillators
Classically, the harmonic oscillator has a potential energy of
V(x) =12
kx2 (0.71.20)
So the force experienced by this particle is
F = −dVdx
= −kx (0.71.21)
where k is the spring constant. The equation of motion can be summed us as
md2xdt2 = −kx (0.71.22)
And the solution of this equation is
x(t) = A cos(ω0t + φ
)(0.71.23)
where the angular frequency, ω0 is
ω0 =
√km
(0.71.24)
The Quantum Mechanical description on the harmonic oscillator is based on the eigen-function solutions of the time-independent Schrodinger’s equation. By taking V(x)from eq. (0.71.20) we substitute into eq. (0.71.9) to get
d2ψ
dx2 =2m~2
(k2
x2− E
)ψ =
mk~2
(x2−
2Ek
)ψ
©2009 David S. Latchman
DRAFT
lii Quantum MechanicsWith some manipulation, we get
~√
mk
d2ψ
dx2 =
√mk~
x2−
2E~
√mk
ψThis step allows us to to keep some of constants out of the way, thus giving us
ξ2 =
√mk~
x2 (0.71.25)
and λ =2E~
√mk
=2E~ω0
(0.71.26)
This leads to the more compact
d2ψ
dξ2 =(ξ2− λ
)ψ (0.71.27)
where the eigenfunction ψ will be a function of ξ. λ assumes an eigenvalue anaglaousto E.
From eq. (0.71.25), we see that the maximum value can be determined to be
ξ2max =
√mk~
A2 (0.71.28)
Using the classical connection between A and E, allows us to say
ξ2max =
√mk~
2Ek
= λ (0.71.29)
From eq. (0.71.27), we see that in a quantum mechanical oscillator, there are non-vanishing solutions in the forbidden regions, unlike in our classical case.
A solution to eq. (0.71.27) isψ(ξ) = e−ξ
2/2 (0.71.30)
where
dψdξ
= −ξe−ξ2/2
anddψ
dξ2 = ξ2e−xi2/2− e−ξ
2/2 =(ξ2− 1
)e−ξ
2/2
This gives is a special solution for λ where
λ0 = 1 (0.71.31)
Thus eq. (0.71.26) gives the energy eigenvalue to be
E0 =~ω0
2λ0 =
~ω0
2(0.71.32)
David S. Latchman ©2009
DRAFT
Schrodinger Equation liiiThe eigenfunction e−ξ2/2 corresponds to a normalized stationary-state wave function
Ψ0(x, t) =
(mkπ2~2
) 18
e−√
mk x2/2~e−iE0t/~ (0.71.33)
This solution of eq. (0.71.27) produces the smallest possibel result of λ and E. Hence,Ψ0 and E0 represents the ground state of the oscillator. and the quantity ~ω0/2 is thezero-point energy of the system.
0.71.3 Finite Square Well
For the Finite Square Well, we have a potential region where
V(x) =
−V0 for −a ≤ x ≤ a0 for |x| > a
We have three regions
Region I: x < −a In this region, The potential, V = 0, so Schrodinger’s Equation be-comes
−~2
2md2ψ
dx2 = Eψ
⇒d2ψ
dx2 = κ2ψ
where κ =
√−2mE~
This gives us solutions that are
ψ(x) = A exp(−κx) + B exp(κx)
As x → ∞, the exp(−κx) term goes to ∞; it blows up and is not a physicallyrealizable function. So we can drop it to get
ψ(x) = Beκx for x < −a (0.71.34)
Region II: −a < x < a In this region, our potential is V(x) = V0. Substitutin this intothe Schrodinger’s Equation, eq. (0.71.9), gives
−~2
2md2ψ
dx2 − V0ψ = Eψ
ord2ψ
dx2 = −l2ψ
where l ≡
√2m (E + V0)~
(0.71.35)
We notice that E > −V0, making l real and positive. Thus our general solutionbecomes
ψ(x) = C sin(lx) + D cos(lx) for −a < x < a (0.71.36)
©2009 David S. Latchman
DRAFT
liv Quantum MechanicsRegion III: x > a Again this Region is similar to Region III, where the potential, V = 0.
This leaves us with the general solution
ψ(x) = F exp(−κx) + G exp(κx)
As x→∞, the second term goes to infinity and we get
ψ(x) = Fe−κx for x > a (0.71.37)
This gives us
ψ(x) =
Beκx for x < aD cos(lx) for 0 < x < aFe−κx for x > a
(0.71.38)
0.71.4 Hydrogenic Atoms
c
0.72 Spin
3
0.73 Angular Momentum
4
0.74 Wave Funtion Symmetry
5
0.75 Elementary Perturbation Theory
6
David S. Latchman ©2009
DRAFTAtomic Physics
0.76 Properties of Electrons
1
0.77 Bohr Model
To understand the Bohr Model of the Hydrogen atom, we will take advantage of ourknowlegde of the wavelike properties of matter. As we are building on a classicalmodel of the atom with a modern concept of matter, our derivation is considered to be‘semi-classical’. In this model we have an electron of mass, me, and charge, −e, orbitinga proton. The cetripetal force is equal to the Coulomb Force. Thus
14πε0
e2
r2 =mev2
r(0.77.1)
The Total Energy is the sum of the potential and kinetic energies, so
E = K + U =p2
2me− | f race24πε0r (0.77.2)
We can further reduce this equation by subsituting the value of momentum, which wefind to be
p2
2me=
12
mev2 =e2
8πε0r(0.77.3)
Substituting this into eq. (0.77.2), we get
E =e2
8πε0r−
e2
4πε0r= −
e2
8πε0r(0.77.4)
At this point our classical description must end. An accelerated charged particle, likeone moving in circular motion, radiates energy. So our atome here will radiate energyand our electron will spiral into the nucleus and disappear. To solve this conundrum,Bohr made two assumptions.
1. The classical circular orbits are replaced by stationary states. These stationarystates take discreet values.
DRAFT
lvi Atomic Physics2. The energy of these stationary states are determined by their angular momentum
which must take on quantized values of ~.
L = n~ (0.77.5)
We can find the angular momentum of a circular orbit.
L = m3vr (0.77.6)
From eq. (0.77.1) we find v and by substitution, we find L.
L = e√
m3r4πε0
(0.77.7)
Solving for r, gives
r =L2
mee2/4πε0(0.77.8)
We apply the condition from eq. (0.77.5)
rn =n2~2
mee2/4πε0= n2a0 (0.77.9)
where a0 is the Bohr radius.a0 = 0.53 × 10−10 m (0.77.10)
Having discreet values for the allowed radii means that we will also have discreetvalues for energy. Replacing our value of rn into eq. (0.77.4), we get
En = −me
2n2
(e2
4πε0~
)= −
13.6n2 eV (0.77.11)
0.78 Energy Quantization
3
0.79 Atomic Structure
4
0.80 Atomic Spectra
0.80.1 Rydberg’s Equation
1λ
= RH
( 1n′2−
1n2
)(0.80.1)
David S. Latchman ©2009
DRAFT
Selection Rules lviiwhere RH is the Rydberg constant.
For the Balmer Series, n′ = 2, which determines the optical wavelengths. For n′ = 3, weget the infrared or Paschen series. The fundamental n′ = 1 series falls in the ultravioletregion and is known as the Lyman series.
0.81 Selection Rules
6
0.82 Black Body Radiation
0.82.1 Plank Formula
u( f ,T) =8π~c3
f 3
eh f/kT − 1(0.82.1)
0.82.2 Stefan-Boltzmann Formula
P(T) = σT4 (0.82.2)
0.82.3 Wein’s Displacement Law
λmaxT = 2.9 × 10−3 m.K (0.82.3)
0.82.4 Classical and Quantum Aspects of the Plank Equation
Rayleigh’s Equation
u( f ,T) =8π f 2
c3 kT (0.82.4)
We can get this equation from Plank’s Equation, eq. (0.82.1). This equation is a classicalone and does not contain Plank’s constant in it. For this case we will look at thesituation where h f < kT. In this case, we make the approximation
ex' 1 + x (0.82.5)
Thus the demonimator in eq. (0.82.1) becomes
eh f/kT− 1 ' 1 +
h fkT− 1 =
h fkT
(0.82.6)
©2009 David S. Latchman
DRAFT
lviii Atomic PhysicsThus eq. (0.82.1) takes the approximate form
u( f ,T) '8πhc3 f 3 kT
h f=
8π f 2
c3 kT (0.82.7)
As we can see this equation is devoid of Plank’s constant and thus independent ofquantum effects.
Quantum
At large frequencies, where h f > kT, quantum effects become apparent. We canestimate that
eh f/kT− 1 ' eh f/kT (0.82.8)
Thus eq. (0.82.1) becomes
u( f ,T) '8πhc3 f 3e−h f/kT (0.82.9)
0.83 X-Rays
0.83.1 Bragg Condition
2d sinθ = mλ (0.83.1)
for constructive interference off parallel planes of a crystal with lattics spacing, d.
0.83.2 The Compton Effect
The Compton Effect deals with the scattering of monochromatic X-Rays by atomictargets and the observation that the wavelength of the scattered X-ray is greater thanthe incident radiation. The photon energy is given by
E = hυ =hcλ
(0.83.2)
The photon has an associated momentum
E = pc (0.83.3)
⇒ p =E
c=
hυc
=hλ
(0.83.4)
The Relativistic Energy for the electron is
E2 = p2c2 + m2e c4 (0.83.5)
wherep − p′ = P (0.83.6)
David S. Latchman ©2009
DRAFT
Atoms in Electric and Magnetic Fields lixSquaring eq. (0.83.6) gives
p2− 2p · p′ + p′2 = P2 (0.83.7)
Recall that E = pc and E ′ = cp′, we have
c2p2− 2c2p · p′ + c2p′2 = c2P2
E 2− 2E E ′ cosθ + E ′2 = E2
−m2e c4 (0.83.8)
Conservation of Energy leads to
E + mec2 = E ′ + E (0.83.9)
Solving
E − E ′ = E −mec2
E 2− 2E E ′ + E ′ = E2
− 2Emec2 + m2e c4 (0.83.10)
2E E ′ − 2E E ′ cosθ = 2Emec2− 2m2
e c4 (0.83.11)
Solving leads to
∆λ = λ′ − λ =h
mec(1 − cosθ) (0.83.12)
where λc = hmec
is the Compton Wavelength.
λc =h
mec= 2.427 × 10−12m (0.83.13)
0.84 Atoms in Electric and Magnetic Fields
0.84.1 The Cyclotron Frequency
A test charge, q, with velocity v enters a uniform magnetic field, B. The force acting onthe charge will be perpendicular to v such that
FB = qv × B (0.84.1)
or more simply FB = qvB. As this traces a circular path, from Newton’s Second Law,we see that
FB =mv2
R= qvB (0.84.2)
Solving for R, we getR =
mvqB
(0.84.3)
We also see that
f =qB
2πm(0.84.4)
The frequency is depends on the charge, q, the magnetic field strength, B and the massof the charged particle, m.
©2009 David S. Latchman
DRAFT
lx Atomic Physics0.84.2 Zeeman Effect
The Zeeman effect was the splitting of spectral lines in a static magnetic field. This issimilar to the Stark Effect which was the splitting in the presence in a magnetic field.
In the Zeeman experiment, a sodium flame was placed in a magnetic field and itsspectrum observed. In the presence of the field, a spectral line of frequency, υ0 wassplit into three components, υ0 − δυ, υ0 and υ0 + δυ. A classical analysis of this effectallows for the identification of the basic parameters of the interacting system.
The application of a constant magnetic field, B, allows for a direction in space in whichthe electron motion can be referred. The motion of an electron can be attributed to asimple harmonic motion under a binding force −kr, where the frequency is
υ0 =1
2π
√k
me(0.84.5)
The magnetic field subjects the electron to an additional Lorentz Force, −ev × B. Thisproduces two different values for the angular velocity.
v = 2πrυ
The cetripetal force becomesmev2
r= 4π2υ2rme
Thus the certipetal force is
4π2υ2rme = 2πυreB + kr for clockwise motion
4π2υ2rme = −2πυreB + kr for counterclockwise motion
We use eq. (0.84.5), to emiminate k, to get
υ2−
eB2πme
υ − υ0 = 0 (Clockwise)
υ2 +eB
2πmeυ − υ0 = 0 (Counterclockwise)
As we have assumed a small Lorentz force, we can say that the linear terms in υ aresmall comapred to υ0. Solving the above quadratic equations leads to
υ = υ0 +eB
4πmefor clockwise motion (0.84.6)
υ = υ0 −eB
4πmefor counterclockwise motion (0.84.7)
We note that the frequency shift is of the form
δυ =eB
4πme(0.84.8)
If we view the source along the direction of B, we will observe the light to have twopolarizations, a closckwise circular polarization of υ0 + δυ and a counterclosckwisecircular polarization of υ0 − δυ.
David S. Latchman ©2009
DRAFT
Atoms in Electric and Magnetic Fields lxi0.84.3 Franck-Hertz Experiment
The Franck-Hertz experiment, performed in 1914 by J. Franck and G. L. Hertz, mea-sured the colisional excitation of atoms. Their experiement studied the current ofelectrons in a tub of mercury vapour which revealed an abrupt change in the currentat certain critical values of the applied voltage.2 They interpreted this observation asevidence of a threshold for inelastic scattering in the colissions of electrons in mer-cury atoms.The bahavior of the current was an indication that electrons could losea discreet amount of energy and excite mercury atoms in their passage through themercury vapour. These observations constituted a direct and decisive confirmation ofthe existence os quantized energy levels in atoms.
2Put drawing of Franck-Hertz Setup
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DRAFT
lxii Atomic Physics
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DRAFTSpecial Relativity
0.85 Introductory Concepts
0.85.1 Postulates of Special Relativity
1. The laws of Physics are the same in all inertial frames.
2. The speed of light is the same in all inertial frames.
We can define
γ =1√
1 − u2
c2
(0.85.1)
0.86 Time Dilation
∆t = γ∆t′ (0.86.1)
where ∆t′ is the time measured at rest relative to the observer, ∆t is the time measuredin motion relative to the observer.
0.87 Length Contraction
L =L′
γ(0.87.1)
where L′ is the length of an object observed at rest relative to the observer and L is thelength of the object moving at a speed u relative to the observer.
0.88 Simultaneity
4
DRAFT
lxiv Special Relativity0.89 Energy and Momentum
0.89.1 Relativistic Momentum & Energy
In relativistic mechanics, to be conserved, momentum and energy are defined as
Relativistic Momentump = γmv (0.89.1)
Relativistic EnergyE = γmc2 (0.89.2)
0.89.2 Lorentz Transformations (Momentum & Energy)
p′x = γ(px − β
Ec
)(0.89.3)
p′y = py (0.89.4)
p′z = pz (0.89.5)E′
c= γ
(Ec− βpx
)(0.89.6)
0.89.3 Relativistic Kinetic Energy
K = E −mc2 (0.89.7)
= mc2
1√1 − v2
c2
− 1
(0.89.8)
= mc2 (γ − 1)
(0.89.9)
0.89.4 Relativistic Dynamics (Collisions)
∆P′x = γ(∆Px − β
∆Ec
)(0.89.10)
∆P′y = ∆Py (0.89.11)
∆P′z = ∆Pz (0.89.12)∆E′
c= γ
(∆Ec− β∆Px
)(0.89.13)
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DRAFT
Four-Vectors and Lorentz Transformation lxv0.90 Four-Vectors and Lorentz Transformation
We can represent an event in S with the column matrix, s,
s =
xyz
ict
(0.90.1)
A different Lorents frame, S′, corresponds to another set of space time axes so that
s′ =
x′
y′
z′
ict′
(0.90.2)
The Lorentz Transformation is related by the matrixx′
y′
z′
ict′
=
γ 0 0 iγβ0 1 0 00 0 1 0−iγβ 0 0 γ
xyz
ict
(0.90.3)
We can express the equation in the form
s′ = L s (0.90.4)
The matrix L contains all the information needed to relate position four–vectors forany given event as observed in the two Lorentz frames S and S′. If we evaluate
sTs =[
x y z ict]
xyz
ict
= x2 + y2 + z2− c2t2 (0.90.5)
Similarly we can show that
s′Ts′ = x′2 + y′2 + z′2 − c2t′2 (0.90.6)
We can take any collection of four physical quantities to be four vector provided thatthey transform to another Lorentz frame. Thus we have
b =
bx
by
bz
ibt
(0.90.7)
this can be transformed into a set of quantities of b′ in another frame S′ such that itsatisfies the transformation
b′ = L b (0.90.8)
©2009 David S. Latchman
DRAFT
lxvi Special RelativityLooking at the momentum-Energy four vector, we have
p =
px
py
pz
iE/c
(0.90.9)
Applying the same transformation rule, we have
p′ = L p (0.90.10)
We can also get a Lorentz-invariation relation between momentum and energy suchthat
p′Tp′ = pTp (0.90.11)
The resulting equality gives
p′2x + p′2y + p′2z −E′2
c2 = p2x + p2
y + p2z −
E2
c2 (0.90.12)
0.91 Velocity Addition
v′ =v − u1 − uv
c2
(0.91.1)
0.92 Relativistic Doppler Formula
υ = υ0
√c + uc − u
let r =
√c − uc + u
(0.92.1)
We have
υreceding = rυ0 red-shift (Source Receding) (0.92.2)
υapproaching =υ0
rblue-shift (Source Approaching) (0.92.3)
0.93 Lorentz Transformations
Given two reference frames S(x, y, z, t) and S′(x′, y′, z′, t′), where the S′-frame is movingin the x-direction, we have,
x′ = γ (x − ut) x = (x′ − ut′) (0.93.1)y′ = y y = y′ (0.93.2)z′ = y y′ = y (0.93.3)
t′ = γ(t −
uc2 x
)t = γ
(t′ +
uc2 x′
)(0.93.4)
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DRAFT
Space-Time Interval lxvii0.94 Space-Time Interval
(∆S)2 = (∆x)2 +(∆y
)2+ (∆z)2
− c2 (∆t)2 (0.94.1)
Space-Time Intervals may be categorized into three types depending on their separa-tion. They are
Time-like Interval
c2∆t2 > ∆r2 (0.94.2)
∆S2 > 0 (0.94.3)
When two events are separated by a time-like interval, there is a cause-effectrelationship between the two events.
Light-like Interval
c2∆t2 = ∆r2 (0.94.4)
S2 = 0 (0.94.5)
Space-like Intervals
c2∆t2 < ∆r2 (0.94.6)∆S < 0 (0.94.7)
©2009 David S. Latchman
DRAFT
lxviii Special Relativity
David S. Latchman ©2009
DRAFTLaboratory Methods
0.95 Data and Error Analysis
0.95.1 Addition and Subtraction
x = a + b − c (0.95.1)
The Error in x is(δx)2 = (δa)2 + (δb)2 + (δc)2 (0.95.2)
0.95.2 Multiplication and Division
x =a × b
c(0.95.3)
The error in x is (δxx
)2
=(δaa
)2
+
(δbb
)2
+(δcc
)2
(0.95.4)
0.95.3 Exponent - (No Error in b)
x = ab (0.95.5)
The Error in x isδxx
= b(δaa
)(0.95.6)
0.95.4 Logarithms
Base e
x = ln a (0.95.7)
DRAFT
lxx Laboratory MethodsWe find the error in x by taking the derivative on both sides, so
δx =d ln a
da· δa
=1a· δa
=δaa
(0.95.8)
Base 10
x = log10 a (0.95.9)
The Error in x can be derived as such
δx =d(log a)
daδa
=ln a
ln 10
daδa
=1
ln 10δaa
= 0.434δaa
(0.95.10)
0.95.5 Antilogs
Base e
x = ea (0.95.11)
We take the natural log on both sides.
ln x = a ln e = a (0.95.12)
Applaying the same general method, we see
d ln xdx
δx = δa
⇒δxx
= δa (0.95.13)
Base 10
x = 10a (0.95.14)
David S. Latchman ©2009
DRAFT
Instrumentation lxxiWe follow the same general procedure as above to get
log x = a log 10log x
dxδx = δa
1ln 10
d ln adx
δx = δa
δxx
= ln 10δa (0.95.15)
0.96 Instrumentation
2
0.97 Radiation Detection
3
0.98 Counting Statistics
Let’s assume that for a particular experiment, we are making countung measurementsfor a radioactive source. In this experiment, we recored N counts in time T. Thecounting rate for this trial is R = N/T. This rate should be close to the average rate, R.The standard deviation or the uncertainty of our count is a simply called the
√N rule.
Soσ =√
N (0.98.1)
Thus we can report our results as
Number of counts = N ±√
N (0.98.2)
We can find the count rate by dividing by T, so
R =NT±
√N
T(0.98.3)
The fractional uncertainty of our count is δNN . We can relate this in terms of the count
rate.
δRR
=δNTNT
=δNN
=
√N
N
=1N
(0.98.4)
©2009 David S. Latchman
DRAFT
lxxii Laboratory MethodsWe see that our uncertainty decreases as we take more counts, as to be expected.
0.99 Interaction of Charged Particles with Matter
5
0.100 Lasers and Optical Interferometers
6
0.101 Dimensional Analysis
Dimensional Analysis is used to understand physical situations involving a mis ofdifferent types of physical quantities. The dimensions of a physical quantity areassociated with combinations of mass, length, time, electric charge, and temperature,represented by symbols M, L, T, Q, and θ, respectively, each raised to rational powers.
0.102 Fundamental Applications of Probability and Statis-tics
8
David S. Latchman ©2009
DRAFTGR8677 Exam Solutions
0.103 Motion of Rock under Drag Force
From the information provided we can come up with an equation of motion for therock.
mx = −mg − kv (0.103.1)
If you have seen this type of equation, and solved it, you’d know that the rock’s speedwill asymtotically increase to some max speed. At that point the drag force and theforce due to gravity will be the same. We can best answer this question through analysisand elimination.
A Dividing eq. (0.103.1) by m gives
x = −g −km
x (0.103.2)
We see that this only occurs when x = 0, which only happens at the top of theflight. So FALSE.
B At the top of the flight, v = 0. From eq. (0.103.2)
⇒ x = g (0.103.3)
we see that this is TRUE.
C Again from eq. (0.103.2) we see that the acceleration is dependent on whether therock is moving up or down. If x > 0 then x < −g and if x < 0 then x > −g. So thisis also FALSE.
D If there was no drag (fictional) force, then energy would be conserved and the rockwill return at the speed it started with but there is a drag force so energy is lost.The speed the rock returns is v < v0. Hence FALSE.
E Again FALSE. Once the drag force and the gravitational force acting on the rock isbalanced the rock won’t accelerate.
Answer: (B)
DRAFT
lxxiv GR8677 Exam Solutions0.104 Satellite Orbits
The question states that the astronaut fires the rocket’s jets towards Earth’s center. Weinfer that no extra energy is given to the system by this process. Section 0.7.5, showsthat the only other orbit where the specific energy is also negative is an elliptical one.
Answer: (A)
0.105 Speed of Light in a Dielectric Medium
Solutions to the Electromagnetic wave equation gives us the speed of light in terms ofthe electromagnetic permeability, µ0 and permitivitty, ε0.
c =1
√µ0ε0
(0.105.1)
where c is the speed of light. The speed through a dielectric medium becomes
v =1√µε0
=1√
2.1µ0ε0
=c√
2.1(0.105.2)
Answer: (D)
0.106 Wave Equation
We are given the equation
y = A sin( tT−
xλ
)(0.106.1)
We can analyze and eliminate from what we know about this equation
A The Amplitude, A in the equation is the displacement from equilibrium. So thischoice is incorrect.
B As the wave moves, we seek to keep the(
tT −
xλ
)term constant. So as t increases, we
expect x to increase as well as there is a negative sign in front of it. This meansthat the wave moves in the positive x-direction. This choice is also incorrect.
C The phase of the wave is given by(
tT −
xλ
), we can do some manipulation to show
2π( tT−
xλ
)= 2π f t − kx = 0
= ωt − kx (0.106.2)
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DRAFT
Inelastic Collision and Putty Spheres lxxvOr rather
kx = ωt (0.106.3)
Differentiating eq. (0.106.3) gives us the phase speed, which is
v =λT
(0.106.4)
This is also incorrect
E From eq. (0.106.4) the above we see that is the answer.
Answer: (E)
0.107 Inelastic Collision and Putty Spheres
We are told the two masses coalesce so we know that the collision is inelastic andhence, energy is not conserved. As mass A falls, it looses Potential Energy and gainsKinetic Energy.
Mgh0 =12
Mv20 (0.107.1)
Thusv2
0 = 2gh0 (0.107.2)
Upon collision, momentum is conserved, thus
Mv0 = (3M + M) v1
= 4Mv1
⇒ v1 =v0
4(0.107.3)
The fused putty mass rises, kinetic energy is converted to potential energy and we findour final height.
12
(4M) v21 = 4Mgh1 (0.107.4)
This becomesv2
1 = 2gh1 (0.107.5)
Substituting eq. (0.107.3), we get (v0
4
)2
= 2gh1 (0.107.6)
and substituting, eq. (0.107.2),2gh0
16= 2gh1 (0.107.7)
Solving for h1,
h1 =h0
16(0.107.8)
Answer: (A)
©2009 David S. Latchman
DRAFT
lxxvi GR8677 Exam Solutions0.108 Motion of a Particle along a Track
As the particle moves from the top of the track and runs down the frictionless track,its Gravitational Potential Energy is converted to Kinetic Energy. Let’s assume that theparticle is at a height, y0 when x = 0. Since energy is conserved, we get3
mgy0 = mg(y0 − y) +12
mv2
⇒12
v2 = gy (0.108.1)
So we have a relationship between v and the particle’s position on the track.
The tangential acceleration in this case is
mg cosθ =mv2
r(0.108.2)
where r is the radius of curvature and is equal to√
x2 + y2 .
Substituting this into eq. (0.108.2) gives
g cosθ =v2
r
=gx2
2√
x2 + y2
=gx
√
x2 + 4(0.108.3)
Answer: (D)
0.109 Resolving Force Components
This question is a simple matter of resolving the horizontal and vertical componentsof the tension along the rope. We have
T sinθ = F (0.109.1)T cosθ = mg (0.109.2)
Thus we get
tanθ =F
mg
=10
(2)(9.8)≈
12
(0.109.3)
Answer: (A)3Insert Free Body Diagram of particle along track.
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DRAFT
Nail being driven into a block of wood lxxvii0.110 Nail being driven into a block of wood
We recall thatv2 = v2
0 + 2as (0.110.1)
where v, v0, a and s are the final speed, initial speed, acceleration and displacementthat the nail travels. Now it’s just a matter of plugging in what we know
0 = 100 + 2a(0.025)
⇒ a = −100
2(0.025)= −2000 m s−2 (0.110.2)
The Force on the nail comes from Newton’s Second Law
F = ma= 5 · 2000 = 10 000 N (0.110.3)
Answer: (D)
0.111 Current Density
We can find the drift velocity from the current density equation
J = envd (0.111.1)
where e is the charge of an electron, n is the density of electrons per unit volume andvd is the drift speed. Plugging in what we already know
J =IA
I =nAvde
vd =I
nAe
=100
(1 × 1028)π × 2 × 10−4
41.6 × 10−19
(0.111.2)
paying attention to the indices of the equation we get
2 − 28 + 4 + 19 = −4 (0.111.3)
So we expect an answer where vd ≈ 10−4 m s−1.4
Answer: (D)4It also helps if you knew that the electron drift velocity was slow, in the order of mm/s.
©2009 David S. Latchman
DRAFT
lxxviii GR8677 Exam Solutions0.112 Charge inside an Isolated Sphere
You can answer this by thinking about Gauss’ Law. The bigger the Gaussian surfacethe more charge it encloses and the bigger the electric field. Beyond the radius of thesphere, the field decreases exponentially5.
We can calculate these relationships by using Gauss’ Law.∮S
E · dS =Qenclosed
ε0(0.112.1)
where the current density, ρ is
ρ =Q
43πR3
=Qenclosed
43πr3
(0.112.2)
where R is the radius of the sphere.
for r < R The enclosed charge becomes
Qenclosed = ρ(43πr3
)=
Qr3
R3 (0.112.3)
Gauss’ Law becomes
E(4πr2
)=
Qr3
ε0R3 (0.112.4)
The Electric field is
E(r<R) =Qr
4πε0R3 (0.112.5)
This is a linear relationship with respect to r.
for r ≥ R The enclosed charge isQenclosed = Q (0.112.6)
Gauss’ Law becomes
E(4πr2
)=
Qε0
(0.112.7)
The Electric field is
E(r≥R) =Q
4πε0r2 (0.112.8)
The linear increase is exhibited by choice (C).
Answer: (C)
5Draw diagrams.
David S. Latchman ©2009
DRAFT
Vector Identities and Maxwell’s Laws lxxix0.113 Vector Identities and Maxwell’s Laws
We recall the vector identity∇ · (∇ ×A) = 0 (0.113.1)
Thus
∇ · (∇ ×H) = ∇ ·(D + J
)= 0 (0.113.2)
Answer: (A)
0.114 Doppler Equation (Non-Relativistic)
We recall the Doppler Equation6
f = f0
(v − vr
v − vs
)(0.114.1)
where vr and vs are the observer and source speeds respectively. We are told that vr = 0and vs = 0.9v. Thus
f = f0
( vv − 0.9v
)= 10 f0
= 10 kHz (0.114.2)
Answer: (E)
0.115 Vibrating Interference Pattern
Answering this question takes some analysis. The sources are coherent, so they willproduce an interference pattern. We are also told that ∆ f = 500 Hz. This will producea shifting interference pattern that changes too fast for the eye to see.7
Answer: (E)
0.116 Specific Heat at Constant Pressure and Volume
From section 0.65 and section 0.66, we see that
Cp = CV + R (0.116.1)
6Add reference to Dopler Equations.7Add Young’s Double Slit Experiment equations.
©2009 David S. Latchman
DRAFT
lxxx GR8677 Exam SolutionsThe difference is due to the work done in the environment by the gas when it expandsunder constant pressure.
We can prove this by starting with the First Law of Thermodynamics.
dU = −dW + dQ (0.116.2)
Where dU is the change in Internal Energy, dW is the work done by the system and dQis the change in heat of the system.
We also recall the definition for Heat Capacity
dQ = CdT (0.116.3)
At constant volume, there is no work done by the system, dV = 0. So it follows thatdW = 0. The change in internal energy is the change of heat into the system, thus wecan define, the heat capacity at constant volume to be
dUV = CVdT = dQV (0.116.4)
At constant pressure, the change in internal energy is accompanied by a change in heatflow as well as a change in the volume of the gas, thus
dUp = −dWp + dQp
= −pdV + CpdT where pdV = nRdT= −nRdT + CpdT (0.116.5)
If the changes in internal energies are the same in both cases, then eq. (0.116.5) is equalto eq. (0.116.4). Thus
CVdT = −nRdT + CpdT
This becomesCp = CV + nR (0.116.6)
We see the reason why Cp > CV is due to the addition of work on the system; eq. (0.116.4)shows no work done by the gas while eq. (0.116.5) shows that there is work done.
Answer: (A)
0.117 Helium atoms in a box
Let’s say the probability of the atoms being inside the box is 1. So the probability thatan atom will be found outside of a 1.0 × 10−6 cm3 box is
P = 1 − 1.0 × 10−6 (0.117.1)
As there are N atoms and the probability of finding one is mutually exclusive of theother, the probabolity becomes
P =(1 − 1.0 × 10−6
)N(0.117.2)
Answer: (C)
David S. Latchman ©2009
DRAFT
The Muon lxxxi0.118 The Muon
It helps knowing what these particles are
Muon The muon, is a lepton, like the electron. It has the ame charge, −e and spin, 1/2,as the electron execpt it’s about 200 times heavier. It’s known as a heavy electron.
Electron This is the answer.
Graviton This is a hypothetical particle that mediates the force of gravity. It has nocharge, no mass and a spin of 2. Nothing like an electron.
Photon The photon is the quantum of the electromagnetic field. It has no charge ormass and a spin of 1. Again nothing like an electron.
Pion The Pion belongs to the meson family. Again, nothing like leptons.
Proton This ia a sub atomic particle and is found in the nucleus of all atoms. Nothinglike an electron.
Answer: (A)
0.119 Radioactive Decay
From the changes in the Mass and Atomic numbers after the subsequent decays, weexpect an α and β decay.
Alpha DecayAZX→A−4
Z−2 X′ +42 α (0.119.1)
Beta DecayAZX→A
Z+1 X′ +−1 e− + υe (0.119.2)
Combining both gives
AZX→A−4
Z−2 X′ +42 α→
AZ−1 Y +−1 e− + υe (0.119.3)
Answer: (B)
©2009 David S. Latchman
DRAFT
lxxxii GR8677 Exam Solutions0.120 Schrodinger’s Equation
We recall that Schrodinger’s Equation is
Eψ = −~2
2m∂2ψ
∂x2 + V(x)ψ (0.120.1)
Given that
ψ(x) = A exp−
b2x2
2
(0.120.2)
We differentiate and get∂2ψ
∂x2 =(b4x2− b2
)ψ (0.120.3)
Plugging into Schrodinger’s Equation, eq. (0.120.1), gives us
Eψ = −~2
2m
(b4x2− b2
)ψ + V(x)ψ (0.120.4)
Applying the boundary condition at x = 0 gives
Eψ =~2
2mb2ψ (0.120.5)
This gives~2b2
2mψ = −
~2
2m
(b4x2− b2
)ψ + V(x)ψ (0.120.6)
Solving for V(x) gives
V(x) =~2b4x2
2m(0.120.7)
Answer: (B)
0.121 Energy Levels of Bohr’s Hydrogen Atom
We recall that the Energy Levels for the Hydrogen atom is
En = −Z2
n2 13.6eV (0.121.1)
where Z is the atomic number and n is the quantum number. This can easily be reducedto
En = −An2 (0.121.2)
Answer: (E)
David S. Latchman ©2009
DRAFT
Relativistic Energy lxxxiii0.122 Relativistic Energy
The Rest Energy of a particle is given
E = mc2 (0.122.1)
The Relativistic Energy is for a relativistic particle moving at speed v
E = γvmc2 (0.122.2)
We are told that a kaon moving at relativistic speeds has the same energy as the restmass as a proton. Thus
EK+ = Ep (0.122.3)
where
EK+ = γvmK+c2 (0.122.4)
Ep = mpc2 (0.122.5)
Equating both together gives
γv =mp
mK+
=939494
≈940500
(0.122.6)
This becomes
γv =
(1 −
v2
c2
)−1/2
≈ 1.88 (0.122.7)
This is going to take some approximations and estimations but(1 −
v2
c2
)−1
= 3.6 (0.122.8)
which works out tov2
c2 = 0.75 (0.122.9)
We expect this to be close to the 0.85c answer.
Answer: (E)
0.123 Space-Time Interval
We recall the Space-Time Interval from section 0.94.
(∆S)2 = (∆x)2 +(∆y
)2+ (∆z)2
− c2 (∆t)2 (0.123.1)
©2009 David S. Latchman
DRAFT
lxxxiv GR8677 Exam SolutionsWe get
∆S2 = (5 − 3)2 + (3 − 3)2 + (3 − 1)2− c2(5 − 3)2
= 22 + 02 + 22− 22
= 22
∆S = 2 (0.123.2)
Answer: (C)
0.124 Lorentz Transformation of the EM field
Lorentz transformations show that electric and magnetic fields are different aspects ofthe same force; the electromagnetic force. If there was one stationary charge in ourrest frame, we would observe an electric field. If we were to move to a moving frameof reference, Lorentz transformations predicts the presence of an additional magneticfield.
Answer: (B)
0.125 Conductivity of a Metal and Semi-Conductor
More of a test of what you know.
A Copper is a conductor so we expect its conductivity to be much greater than that ofa semiconductor. TRUE.
B As the temperature of the conductor is increased its atoms vibrate more and disruptthe flow of electrons. As a result, resistance increases. TRUE.
C Different process. As temperature increases, electrons gain more energy to jump theenergy barrier into the conducting region. So conductivity increases. TRUE.
D You may have paused to think for this one but this is TRUE. The addition of animpurity causes an increase of electron scattering off the impurity atoms. As aresult, resistance increases.8
E The effect of adding an impurity on a semiconductor’s conductivity depends onhow many extra valence electrons it adds or subtracts; you can either widen ornarrow the energy bandgap. This is of crucial importance to electronics today.So this is FALSE.
Answer: (E)8There are one or two cases where this is not true. The addition of Silver increases the conductivity
of Copper. But the conductivity will still be less than pure silver.
David S. Latchman ©2009
DRAFT
Charging a Battery lxxxv0.126 Charging a Battery
The Potential Difference across the resistor, R is
PD = 120 − 100 = 20 V (0.126.1)
The Total Resistance is
R + r =VI
=2010
R + 1 = 2⇒ R = 1 Ω (0.126.2)
Answer: (C)
0.127 Lorentz Force on a Charged Particle
We are told that the charged particle is released from rest in the electric and magneticfields. The charged particle will experience a force from the magnetic field only whenit moves perpendicular to the direction of the magnetic field lines. The particle willmove along the direction of the electric field.
We can also anylize this by looking at the Lorentz Force equation
Fq = q [E + (v × B)] (0.127.1)
v is in the same direction as B so the cross product between them is zero. We are leftwith
Fq = qE (0.127.2)
The force is directed along the electrical field line and hence it moves in a straight line.
Answer: (E)
0.128 K-Series X-Rays
To calculate we look at the energy levels for the Bohr atom. As the Bohr atom considersthe energy levels for the Hydrogen atom, we need to modify it somewhat
En = Z2eff
1n2
f
−1n2
i
13.6eV (0.128.1)
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lxxxvi GR8677 Exam Solutionswhere Zeff is the effective atomic number and n f and ni are the energy levels. For then f = 1 transition
Zeff = Z − 1 (0.128.2)
where Z = 28 for nickle. As the electrons come in from ni = ∞, eq. (0.128.1) becomes
E1 = (28 − 1)2[ 112 −
1∞2
]13.6eV (0.128.3)
This works out to
E1 = (272)13.6eV
≈ (30)2× 13.6eV (0.128.4)
This takes us in the keV range.
Answer: (D)
0.129 Electrons and Spin
It helps if you knew some facts here.
A The periodic table’s arrangement of elements tells us about the chemical propertiesof an element and these properties are dependent on the valent electrons. Howthese valent electrons are arranged is, of course, dependent on spin. So thischoice is TRUE.
B The energy of an electron is quantized and obey the Pauli’s Exclusion Principle. Allthe electrons are accommodated from the lowest state up to the Fermi Level andthe distribution among levels is described by the Fermi distribution function,f (E), which defines the probability that the energy level, E, is occupied by anelectron.
f (E) =
1, E < EF
0, E > EF
where f (E) is the Fermi-Dirac Distribution
f (E) =1
eE−EF/kT + 1(0.129.1)
As a system goes above 0K, thermal energy may excite to higher energy statesbut this energy is not shared equally by all the electrons. The way energy isdistributed comes about from the exclusion principle, the energy an electron myabsorb at room temperature is kT which is much smaller than EF = 5eV. We candefine a Fermi Temperature,
EF = kTF (0.129.2)
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Normalizing a wavefunction lxxxviiwhich works out to be, TF = 60000K. Thus only electrons close to this temperaturecan be excited as the levels above EF are empty. This results in a small number ofelectrons being able to be thermally excited and the low electronic specific heat.
C =π2
2Nk
(TT f
)where kT << EF
So this choice is also TRUE.
C The Zeeman Effect describes what happens to Hydrogen spectral lines in a magneticfield; the spectral lines split. In some atoms, there were further splits in spectrallines that couldn’t be explained by magnetic dipole moments. The explanationfor this additional splitting was discovered to be due to electron spin.9
D The deflection of an electron in a uniform magnetic field deflects only in one wayand demonstrates none of the electron’s spin properties. Electrons can be de-flected depending on their spin if placed in a non-uniform magnetic field, as wasdemonstrated in the Stern-Gerlach Experiment.10
E When the Hydrogen spectrum is observed at a very high resolution, closely spaceddoublets are observed. This was one of the first experimental evidence for electronspin.11
Answer: (D)
0.130 Normalizing a wavefunction
We are givenψ(φ) = Aeimφ (0.130.1)
Normalizing a function means ∫∞
−∞
|Ψ(x)|2 dx = 1 (0.130.2)
In this case, we want ∫ 2π
0
∣∣∣ψ(φ)∣∣∣2 dφ = 1 (0.130.3)
and that ∣∣∣ψ(x)∣∣∣2 = ψ∗(x)ψ(x) (0.130.4)
9Write up on Zeeman and anomalous Zeemen effects10Write up on Stern-Gerlach Experiment11Write up on Fine Structure
©2009 David S. Latchman
DRAFT
lxxxviii GR8677 Exam SolutionsSo
⇒
∣∣∣ψ(φ)∣∣∣2 = A2eimφe−imφ
A2∫ 2π
0dφ = 1
A2 [2π − 0] = 1
⇒ A =1√
2π(0.130.5)
0.131 Right Hand Rule
First we use the ‘Grip’ rule to tell what direction the magnetic field lines are going.Assuming the wire and current are coming out of the page, the magnetic field is in aclockwise direction around the wire. Now we can turn to Fleming’s Right Hand Rule,to solve the rest of the question.
As we want the force acting on our charge to be parallel to the current direction, wesee that this will happen when the charge moves towards the wire12.
Answer: (A)
0.132 Electron Configuration of a Potassium atom
We can alalyze and eliminate
A The n = 3 shell has unfilled d-subshells. So this is NOT TRUE.
B The 4s subshell only has one electron. The s subshell can ‘hold’ two electrons so thisis also NOT TRUE.
C Unknown.
D The sum of all the electrons, we add all the superscripts, gives 19. As this is aground state, a lone potassium atom, we can tell that the atomic number is 19.So this is NOT TRUE.
E Potassium has one outer electron, like Hydrogen. So it will also have a sphericallysymmetrical charge distribution.
12Don’t forget to bring your right hand to the exam
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DRAFT
Photoelectric Effect I lxxxix0.133 Photoelectric Effect I
We are given|eV| = hυ −W (0.133.1)
We recall that V is the stopping potential, the voltage needed to bring the current tozero. As electrons are negatively charged, we expect this voltage to be negative.
Answer: (A)
0.134 Photoelectric Effect II
Some history needs to be known here. The photoelectric effect was one of the exper-iments that proved that light was absorbed in discreet packets of energy. This is theexperimental evidence that won Einstein the Nobel Prize in 1921.
Answer: (D)
0.135 Photoelectric Effect III
The quantity W is known as the work function of the metal. This is the energy that isneeded to just liberate an electron from its surface.
Answer: (D)
0.136 Potential Energy of a Body
We recall that
F = −dUdx
(0.136.1)
Given thatU = kx4 (0.136.2)
The force on the body becomes
F = −d
dxkx4
= −4kx3 (0.136.3)
Answer: (B)
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DRAFT
xc GR8677 Exam Solutions0.137 Hamiltonian of a Body
The Hamiltonian of a body is simply the sum of the potential and kinetic energies.That is
H = T + V (0.137.1)
where T is the kinetic energy and V is the potential energy. Thus
H =12
mv2 + kx4 (0.137.2)
We can also express the kinetic energy in terms of momentum, p. So
H =p2
2m+ kx4 (0.137.3)
Answer: (A)
0.138 Principle of Least Action
Hamilton’s Principle of Least Action13 states
Φ =
∫T
(T(q(t), q(t)
)− V
(q(t)
))dt (0.138.1)
where T is the kinetic energy and V is the potential energy. This becomes
Φ =
∫ t2
t1
(12
mv2− kx4
)dt (0.138.2)
Answer: (A)
0.139 Tension in a Conical Pendulum
This is a simple case of resolving the horizontal and vertical components of forces. Sowe have
T cosθ = mg (0.139.1)T sinθ = mrω2 (0.139.2)
Squaring the above two equations and adding gives
T2 = m2g2 + m2r2ω4 (0.139.3)
Leaving us withT = m
(g2 + r2ω4
)(0.139.4)
Answer: (E)13Write something on this
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DRAFT
Diode OR-gate xci0.140 Diode OR-gate
This is an OR gate and can be illustrated by the truth table below.
Input 1 Input 2 Output
0 0 00 1 11 0 11 1 1
Table 0.140.1: Truth Table for OR-gate
Answer: (A)
0.141 Gain of an Amplifier vs. Angular Frequency
We are given that the amplifier has some sort of relationship where
G = Kωa (0.141.1)
falls outside of the amplifier bandwidth region. This is that ‘linear’ part of the graphon the log-log graph. From the graph, we see that, G = 102, for ω = 3 × 105 second-1.Substituting, we get
102 = K(3 × 105
)a
∴ log(102) = a log[K
(3.5 × 105
)]⇒ a ≈ 2 − 5 (0.141.2)
We can roughly estimate by subtracting the indices. So our relationship is of the form
G = Kω−2 (0.141.3)
Answer: (E)
0.142 Counting Statistics
We recall from section 0.98 , that he standard deviation of a counting rate is σ =√
N ,where N is the number of counts. We have a count of N = 9934, so the standarddeviation is
σ =√
N =√
9934
≈
√
10000= 100 (0.142.1)
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DRAFT
xcii GR8677 Exam SolutionsAnswer: (A)
0.143 Binding Energy per Nucleon
More of a knowledge based question. Iron is the most stable of all the others.14
Answer: (C)
0.144 Scattering Cross Section
We are told the particle density of our scatterer is ρ = 1020 nuclei per cubic centimeter.Given the thickness of our scatterer is ` = 0.1 cm, the cross sectional area is
ρ =NV
=NA`
⇒ A =Nρ`
(0.144.1)
Now the probability of striking a proton is 1 in a million. So
A =1 × 10−6
1020× 0.1
= 10−25 cm2 (0.144.2)
Answer: (C)
0.145 Coupled Oscillators
There are two ways this system can oscillate, one mass on the end moves a lot and theother two move out of in the opposite directions but not as much or the centermasscan be stationary and the two masses on the end move out of phase with each other. Inthe latter case, as there isn’t any energy transfer between the masses, the period wouldbe that of a single mass-spring system. The frequency of this would simply be
f =1
2π
√km
(0.145.1)
where k is the spring constant and m is the mass.
Answer: (B)14Write up on Binding Energy
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DRAFT
Coupled Oscillators xciii0.145.1 Calculating the modes of oscillation
In case you require a more rigorous approach, we can calculate the modes of oscillation.The Lagrangian of the system is
L = T − V
=12
m[x2
1 + 2x22 + x2
3
]−
12
k[(x2 − x2)2 + (x3 − x2)2
](0.145.2)
The equation of motion can be found from
ddt
(∂L∂xn
)=∂L∂xn
(0.145.3)
The equations of motion are
mx1 = k (x2 − x1) (0.145.4)2mx2 = kx1 − 2kx2 + kx3 (0.145.5)mx3 = −k (x3 − x2) (0.145.6)
The solutions of the equations are
x1 = A cos(ωt) x2 = B cos(ωt) x3 = C cos(ωt)x1 = −ω2x1 x2 = −ω2x2 x3 = −ω2x3
(0.145.7)
Solving this, we get (k −mω2
)x1 − kx2 = 0 (0.145.8)
−kx1 +(2k − 2mω2
)x2 − kx3 = 0 (0.145.9)
−kx2 +(k −mω2
)x3 = 0 (0.145.10)
We can solve the modes of oscillation by solving∣∣∣∣∣∣∣∣k −mω2
−k 0−k 2k − 2mω2
−k0 −k k −mω2
∣∣∣∣∣∣∣∣ = 0 (0.145.11)
Finding the determinant results in(k −mω2
) [2(k −mω2
)2− k2
]− k
[k(k −mω2
)](0.145.12)
Solving, we get
ω =km
;km±
√2 k
m(0.145.13)
Substituting ω = k/m into the equations of motion, we get
x1 = −x3 (0.145.14)x2 = 0 (0.145.15)
We see that the two masses on the ends move out of phase with each other and themiddle one is stationary.
©2009 David S. Latchman
DRAFT
xciv GR8677 Exam Solutions0.146 Collision with a Rod
Momentum will be conserved, so we can say
mv = MV
V =mvM
(0.146.1)
Answer: (A)
0.147 Compton Wavelength
We recall from section 0.83.2, the Compton Equation from eq. (0.83.12)
∆λ = λ′ − λ =h
mc(1 − cosθ) (0.147.1)
Let θ = 90, we get the Compton Wavelength
λc =h
mc(0.147.2)
where m is the mass of the proton, mp, thus
λc =h
mpc(0.147.3)
Answer: (C)
0.148 Stefan-Boltzmann’s Equation
We recall the Stefan-Boltzmann’s Equation, eq. (0.61.1)
P(T) = σT4 (0.148.1)
At temperature, T1,P1 = σT1 = 10 mW (0.148.2)
We are given T2 = 2T1, so
P2 = σT42
= σ (2T1)4
= 16T41
= 16P1 = 160 mW (0.148.3)
Answer: (E)
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DRAFT
Franck-Hertz Experiment xcv0.149 Franck-Hertz Experiment
The Franck-Hertz Experiment as seen in section 0.84.3 deals with the manner in whichelectrons of certain energies scatter or collide with Mercury atoms. At certain energylevels, the Mercury atoms can ‘absorb’ the electrons energy and be excited and thisoccurs in discreet steps.
Answer: (C)
0.150 Selection Rules for Electronic Transitions
We recall the selection rules for photon emission
∆` = ±1 Orbital angular momentum∆m` = 0,±1 Magnetic quantum number∆ms = 0 Secondary spin quantum number,∆ j = 0,±1 Total angular momentum
NOT FINISHED
Answer: (D)
0.151 The Hamilton Operator
The time-independent Schrodinger equation can be written
Hψ = Eψ (0.151.1)
We can determine the energy of a quantum particle by regarding the classical nonrel-ativistic relationship as an equality of expectation values.
〈H〉 =
⟨p2
2m
⟩+ 〈V〉 (0.151.2)
We can solve this through the substition of a momentum operator
p→~
i∂∂x
(0.151.3)
Substituting this into eq. (0.151.2) gives us
〈H〉 =
∫ +∞
−∞
ψ∗[−~
2m∂2
∂x2ψ + V(x)ψ]
dx
=
∫ +∞
−∞
ψ∗i~∂∂tψdx (0.151.4)
©2009 David S. Latchman
DRAFT
xcvi GR8677 Exam SolutionsWe know from the Schrodinger Time Dependent Equation
−~2
2m∂2Ψ
∂x2 + V(x)Ψ = i~∂Ψ∂t
(0.151.5)
So we can get a Hamiltonian operator
H→ i~∂∂t
(0.151.6)
Answer: (B)
0.152 Hall Effect
The Hall Effect describes the production of a potential difference across a currentcarrying conductor that has been placed in a magnetic field. The magnetic field isdirected perpendicularly to the electrical current.
As a charge carrier, an electron, moves through the conductor, the Lorentz Force willcause a deviation in the carge carrier’s motion so that more charges accumulate in onelocation than another. This asymmetric distribution of charges produces an electricfield that prevents the build up of more electrons. This ‘equilibrium’ voltage across theconductor is known as the Hall Voltage and remains as long as a current flows throughour conductor.
As the deflection and hence, the Hall Voltage, is determined by the sign of the carrier,this can be used to measure the sign of charge carriers.
An equilibrium condition is reached when the electric force, generated by the accumu-lated charge carriers, is equal the the magnetic force, that causes the accumulation ofcharge carriers. Thus
Fm = evdB Fe = eE (0.152.1)
The current through the conductor is
I = nAvde (0.152.2)
For a conductor of width, w and thickness, d, there is a Hall voltage across the widthof the conductor. Thus the electrical force becomes
Fe = eE
=EVH
w(0.152.3)
The magnetic force is
Fm =BI
neA(0.152.4)
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Debye and Einstein Theories to Specific Heat xcviieq. (0.152.3) is equal to eq. (0.152.4), thus
eVH
w=
BInewd
∴ VH =BIned
(0.152.5)
So for a measured magnetic field and current, the sign of the Hall voltage gives is thesign of the charge carrier.
Answer: (C)
0.153 Debye and Einstein Theories to Specific Heat
The determination of the specific heat capacity was first deermined by the Law ofDulong and Petite. This Law was based on Maxwell-Boltzmann statistics and wasaccurate in its predictions except in the region of low temperatures. At that point thereis a departure from prediction and measurements and this is where the Einstein andDebye models come into play.
Both the Einstein and Debye models begin with the assumption that a crystal is madeup of a lattice of connected quantum harmonic oscillators; choice B.
The Einstein model makes three assumptions
1. Each atom is a three-dimensional quantum harmonic oscillator.
2. Atoms do not interact with each other.
3. Atoms vibrate with the same frequency.
Einstein assumed a quantum oscillator model, similar to that of the black body radi-ation problem. But despite its success, his theory predicted an exponential decress inheat capacity towards absolute zero whereas experiments followed a T3 relationship.This was solved in the Debye Model.
The Debye Model looks at phonon contribution to specific heat capacity. This theorycorrectly predicted the T3 proportionality at low temperatures but suffered at inteme-diate temperatures.
Answer: (B)
0.154 Potential inside a Hollow Cube
By applying Gauss’ Law and drawing a Gaussian surface inside the cube, we see thatno charge is enclosed and hence no electric field15. We can realte the electric field to
15Draw Cube at potential V with Gaussian Surface enclosing no charge
©2009 David S. Latchman
DRAFT
xcviii GR8677 Exam Solutionsthe potential
E = −∇V (0.154.1)
Where V is the potential.
Gauss’ Law shows that with no enclosed charge we have no electric field inside ourcube. Thus
E = −∇V = 0 (0.154.2)
As eq. (0.154.1) is equal to zero, the potential is the same throughout the cube.16
Answer: (E)
0.155 EM Radiation from Oscillating Charges
As the charge particle oscillates, the electric field oscillates as well. As the field oscillatesand changes, we would expect this changing field to affect a distant charge. If weconsider a charge along the xy-plane, looking directly along the x-axis, we won’t “see”the charge oscillating but we would see it clearly if we look down the y-axis. If wewere to visualize the field, it would look like a doughnut around the x-axis. Based onthat analysis, we choose (C)
Answer: (C)
0.156 Polarization Charge Density
D = ε0E + P (0.156.1)
∇ ·D = ε0∇ · E + ∇ · P
=εD∇ · Eκ
− σp
Answer: (E)17
0.157 Kinetic Energy of Electrons in Metals
Electrons belong to a group known as fermions18 and as a result obey the Pauli Exclu-sion Principle19. So in the case of a metal, there are many fermions present each with
16As we expect there to be no Electric Field, we must expect the potential to be the same throughoutthe space of the cube. If there were differences, a charge place inside the cube would move.
17Check Polarization in Griffiths18Examples of fermions include electrons, protons and neutrons19The Pauli Exclusion Principle states that no two fermions may occupy the same quantum state
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DRAFT
Expectation or Mean Value xcixa different set of quantum numbers. The electron with the highest energy state is hasan energy value known as the Fermi Energy.
NOT FINISHED
Answer: (B)
0.158 Expectation or Mean Value
This is a definition question. The question states that for an operator Q,
〈Q〉 =
∫ +∞
−∞
ψ∗Qψdx (0.158.1)
This is the very definition of the expectation or mean value of Q.
Answer: (C)
0.159 Eigenfuction of Wavefunction
We are given the momentum operator as
p = −i~∂∂x
(0.159.1)
With an eigenvalue of ~k. We can do this by trying each solution and seeing if theymatch20
− i~∂ψ
∂x= ~kψ (0.159.2)
A: ψ = cos kx We expect ψ, to have the form of an exponential function. Substitutingthis into the eigenfuntion, eq. (0.159.2), we have
−i~∂∂x
cos kx = −i~ (−k sin kx)
= i~k sin kx , ~kψ
ψ does not surive our differentiation and so we can eliminate it.
B: ψ = sin kx This is a similar case to the one above and we can eliminate for thisreason.
−i~∂∂x
sin kx = −i~ (k cos kx)
= −i~k cos kx , ~kψ
20We can eliminate choices (A) & (B) as we would expect the answer to be an exponential function inthis case. These choices were just done for illustrative purposes and you should know to avoid them inthe exam.
©2009 David S. Latchman
DRAFT
c GR8677 Exam SolutionsAgain we see that ψ does not survive when we apply our operator and so we caneliminate this choice as well.
C: ψ = exp−ikx Substituting this into eq. (0.159.2), gives
−i~∂∂x
e−ikx = −i~(−ike−ikx
)= −~ke−ikx , ~kψ
Close but we are off, so we can eliminate this choice as well.
D: ψ = exp ikx If the above choice didn’t work, this might be more likely to.
−i~∂∂x
eikx = −i~(ikeikx
)= ~ke−ikx = ~kψ
Success, this is our answer.
E: = ψ = exp−kx
−i~∂∂x
e−kx = −i~(−ke−kx
)= −i~ke−kx , ~kψ
Again this choice does not work, so we can eliminate this as well
Answer: (D)
0.160 Holograms
The hologram is an image that produces a 3-dimensional image using both the Am-plitude and Phase of a wave. Coherent, monochromatic light, such as from a laser, issplit into two beams. The object we wish to “photograph” is placed in the path of theillumination beam and the scattered light falls on the recording medium. The secondbeam, the reference beam is reflected unimpeded to the recording medium and thesetwo beams produces an interference pattern.
The intensity of light recorded on our medium is the same as the scattered light fromour object. The interference pattern is a result of phase changes as light is scattered offour object. Thus choices (I) and (II) are true.
Answer: (B)
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DRAFT
Group Velocity of a Wave ci0.161 Group Velocity of a Wave
We are given the dispersion relationship of a wave as
ω2 =(c2k2 + m2
) 12 (0.161.1)
The Group Velocity of a Wave is
vg =dωdk
(0.161.2)
By differentiating eq. (0.161.1) with respect to k, we can determine th group velocity
2ωdω = 2c2kdk
⇒dωdk
=c2kω
=c2k
√
c2k2 + m2(0.161.3)
We want to examine the cases as k→ 0 and k→∞.
As k→ 0, we have
dωdk
=c20
√0 + m2
= 0 (0.161.4)
As k→∞, c2k2 >> m2 the denominator becomes√
c2k2 + m ≈ c2k2 (0.161.5)
Replacing the denominator for our group velocity gives
dωdk
=c2kck
= c (0.161.6)
Answer: (E)
0.162 Potential Energy and Simple Harmonic Motion
We are given a potential energy of
V(x) = a + bx2 (0.162.1)
We can determine the mass’s spring constant, k, from V′′(x)
V′′(x) = 2b = k (0.162.2)
The angular frequency, ω, is
ω2 =km
=2bm
(0.162.3)
We see this is dependent on b and m.
Answer: (C)
©2009 David S. Latchman
DRAFT
cii GR8677 Exam Solutions0.163 Rocket Equation I
We recall from the rocket equation that u in this case is the speed of the exaust gasrelative to the rocket.
Answer: (E)
0.164 Rocket Equation II
The rocket equation is
mdvdt
+ udmdt
= 0 (0.164.1)
Solving this equation becomes
mdv = udm∫ v
0dv = u
∫ m
m0
dmm
v = u ln( mm0
)(0.164.2)
This fits none of the answers given.
Answer: (E)
0.165 Surface Charge Density
This question was solved as ‘The Classic Image Problem’. Below is an alternativemethod but the principles are the same. Instead of determining the electrical potential,as was done by Griffiths, we will find the electrical field of a dipole and determine thesurface charge density using
E =σε0
(0.165.1)
Our point charge,−q will induce a +q on the grounded conducting plane. The resultingelectrical field will be due to a combination of the real charge and the ‘virtual’ inducedcharge. Thus
E = −Eyj = (E− + E+) j
= 2E−j (0.165.2)
Remember the two charges are the same, so at any point along the x-axis, or rather ourgrounded conductor, the electrical field contributions from both charges will be the
David S. Latchman ©2009
DRAFT
Maximum Power Theorem ciiisame. Thus
E− =q
4πεr2 cosθ where cosθ =dr
=qd
4πε0r3 (0.165.3)
Our total field becomes
E =2qd
4πε0r3 (0.165.4)
You may recognize that 2qd is the electrical dipole moment. Now, putting eq. (0.165.4)equal to eq. (0.165.1) gives us
σε0
=qd
2πε0r3 (0.165.5)
where r = D, we get
σ =qd
2πD2 (0.165.6)
Answer: (C)
0.166 Maximum Power Theorem
We are given the impedance of our generator
Zg = Rg + jXg (0.166.1)
For the maximum power to be transmitted, the maximum power theorem states that theload impedance must be equal to the complex conjugate of the generator’s impedance.
Zg = Z∗` (0.166.2)
Thus
Z` = Rg + jX`
= Rg − jXg (0.166.3)
Answer: (C)
0.167 Magnetic Field far away from a Current carryingLoop
The Biot-Savart Law is
dB =µ0i4π
d` × rr3 (0.167.1)
©2009 David S. Latchman
DRAFT
civ GR8677 Exam SolutionsLet θ be the angle between the radius, b and the radius vector, r, we get
B =µ0i4π
rd` cosθr3 where cosθ =
br
=mu0i4π
d` cosθr2
=µ0i4π
bd`r3 where r =
√
b2 + h2
=µ0i4π
bd`
(b2 + h2)32
where d` = b · dθ
=µ0i4π·
b2
(b2 + h2)32
2π∫0
dθ
=µ0i2
b2
(b2 + h2)32
(0.167.2)
we see thatB ∝ ib2 (0.167.3)
Answer: (B)
0.168 Maxwell’s Relations
To derive the Maxwell’s Relations we begin with the thermodynamic potentials
First LawdU = TdS − PdV (0.168.1)
Entalpy
H = E + PV∴ dH = TdS + VdP (0.168.2)
Helmholtz Free Energy
F = E − TS∴ dF = −SdT − PdV (0.168.3)
Gibbs Free Energy
G = E − TS + PV∴ dG = −SdT + VdP (0.168.4)
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Partition Functions cvAll of these differentials are of the form
dz =
(∂z∂x
)y
dx +
(∂z∂y
)x
dy
= Mdx + Ndy
For the variables listed, we choose eq. (0.168.1) and applying the above condition weget
T =
(∂U∂S
)V
P =
(∂U∂V
)S
(0.168.5)
Thus taking the inverse of T, gives us
1T
=
(∂S∂U
)V
(0.168.6)
Answer: (E)
0.169 Partition Functions
NOT FINISHED
0.170 Particle moving at Light Speed
Answer: (A)
0.171 Car and Garage I
We are given the car’s length in its rest frame to be L′ = 5 meters and its LorentzContracted length to be L = 3 meters. We can determine the speed from eq. (0.87.1)
L = L′√
1 −v2
c2(35
)2
= 1 −v2
c2
⇒ v =45
c (0.171.1)
Answer: (C)
©2009 David S. Latchman
DRAFT
cvi GR8677 Exam Solutions0.172 Car and Garage II
As the car approaches the garage, the driver will notice that things around him, in-cluding the garage, are length contracted. We have calculated that the speed thathe is travelling at to be, v = 0.8c, in the previous section. We again use the LengthContraction formula, eq. (0.87.1), to solve this question.
Lg = L′g
(1 −
v2
c2
)= 4
(1 − 0.82
)= 2.4 meters (0.172.1)
Answer: (A)
0.173 Car and Garage III
This is more of a conceptual question. What happens depends on whose frame ofreference you’re in.
Answer: (E)
0.174 Refrective Index of Rock Salt and X-rays
No special knowledge is needed but a little knowledge always helps. You can start byeliminating choices when in doubt.
Choice A NOT TRUE Relativity says nothing about whether light is in a vacuum ornot. If anything, this choice goes against the postulates of Special Relativity. Thelaws of Physics don’t change in vacuum.
Choice B NOT TRUE. X-rays can “transmit” signals or energy; any waveform canonce it is not distorted too much during propagation.
Choice C NOT TRUE. Photons have zero rest mass. Though the tachyon, a hypothet-ical particle, has imaginary mass. This allows it to travel faster than the speed orlight though they don’t violate the principles of causality.
Choice D NOT TRUE. How or when we discover physical theories has no bearingon observed properties or behavior; though according to some it may seem so attimes.
Choice E The phase and group speeds can be different. The phase velocity is the rate atwhich the crests of the wave propagate or the rate at which the phase of the waveis moving. The group speed is the rate at which the envelope of the waveform
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Thin Flim Non-Reflective Coatings cviiis moving or rather it’s the rate at which the amplitude varies in the waveform.We can use this principle of n < 1 materials to create X-ray mirrors using “totalexternal reflection”.
Answer: (E)
0.175 Thin Flim Non-Reflective Coatings
To analyze this system, we consider our lens with refractive index, n3, being coated byour non-reflective coating of refractive index, n2, and thickness, t, in air with refractiveindex, n1, where
n1 < n2 < n3 (0.175.1)
As our ray of light in air strikes the first boundary, the coating, it moves from a lessoptically dense medium to a more optically dense one. At the point where it reflects,there will be a phase change in the reflected wave. The transmitted wave goes throughwithout a phase change.
The refracted ray passes through our coating to strike our glass lens, which is opticallymore dense than our coating. As a result there will be a phase change in our reflectedray. Destructive interference occurs when the optical path difference, 2t, occurs inhalf-wavelengths multiples. So
2t =(m +
12
)λn2
(0.175.2)
where m = 0; 1; 2; 3. The thinnest possible coating occurs at m = 0. Thus
t =14λn2
(0.175.3)
We need a non-reflective coating that has an optical thicknes of a quarter wavelength.
Answer: (A)
0.176 Law of Malus
The Law of Malus states that when a perfect polarizer is placed in a polarized beamof light, the intensity I, is given by
I = I0 cos2 θ (0.176.1)
where θ is the angle between the light’s plane of polarization and the axis of thepolarizer. A beam of light can be considered to be a uniform mix of plane polarization
©2009 David S. Latchman
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cviii GR8677 Exam Solutionsangles and the average of this is
I = I0
∫ 2π
0cos2 θ
=12
I0 (0.176.2)
So the maximum fraction of transmitted power through all three polarizers becomes
I3 =(12
)3
=I0
8(0.176.3)
Answer: (B)
0.177 Geosynchronous Satellite Orbit
We can relate the period or the angluar velocity of a satellite and Newton’s Law ofGravitation
mRω2 = mR(2π
T
)2
=GMm
R2 (0.177.1)
where M is the mass of the Earth, m is the satellite mass and RE is the orbital radius.From this we can get a relationship between the radius of orbit and its period, whichyou may recognize as Kepler’s Law.
R3∝ T2 (0.177.2)
We can say
R3E ∝ (80)2 (0.177.3)
R3S ∝ (24 × 60)2 (0.177.4)
(0.177.5)
Dividing eq. (0.177.4) and eq. (0.177.5), gives(RS
RE
)3
=(24 × 60
80
)2
R3S = 182R3
E (0.177.6)
Answer: (B)
0.178 Hoop Rolling down and Inclined Plane
As the hoop rolls down the inclined plane, its gravitational potential energy is con-verted to translational kinetic energy and rotational kinetic energy
Mgh =12
Mv2 +12
Iω2 (0.178.1)
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Simple Harmonic Motion cixRecall that v = ωR, eq. (0.178.1) becomes
MgH =12
MR2ω2 +12
(MR2
)ω2 (0.178.2)
Solving for ω leaves
ω =
(ghR2
) 12
(0.178.3)
The angular momentum isL = Iω (0.178.4)
Substituting eq. (0.178.3) gives us
L = MR(
ghR2
) 12
= MR√
gh (0.178.5)
Answer: (A)
0.179 Simple Harmonic Motion
We are told that a particle obeys Hooke’s Law, where
F = −kx (0.179.1)
We can write the equation of motion as
mx − kx where ω2 =km
where
x = A sin(ωt + φ
)(0.179.2)
and x = ωA cos(ωt + φ
)(0.179.3)
We are told that12
= sin(ωt + φ
)(0.179.4)
We can show that
cos(ωt + φ
)=
√3
2(0.179.5)
Substituting this into eq. (0.179.3) gives
x = 2π f A ·√
32
=√
3 π f A (0.179.6)
Amswer: (B)
©2009 David S. Latchman
DRAFT
cx GR8677 Exam Solutions0.180 Total Energy between Two Charges
We are told three things
1. There is a zero potential energy, and
2. one particle has non-zero speed and hence kinetic energy.
3. No radiation is emitted, so no energy is lost.
The total energy of the system is
E = Potential Energy + Kinetic Energy= 0 + (KE > 0)> 0 (0.180.1)
Applying the three condition, we expect the total energy to be positive and constant.
Answer: (C)
0.181 Maxwell’s Equations and Magnetic Monopoles
You may have heard several things about the∇·B = 0 equation in Maxwell’s Laws. Oneof them is there being no magnetic monopoles or charges. There are some implicationsto this. No charge implies that the amount of field lines that enter a Gaussian surfacemust be equal to the amount of field lines that leave. So using this principle we knowfrom the electric form of this law we can get an answer to this question.
Choice A The number of field lines that enter is the same as the number that leaves.So this does not violate the above law.
Choice B Again we see that the number of field lines entering is the same as thenumber leaving.
Choice C The same as above
Choice D In this case, we see that the field lines at the edge of the Gaussian Surfaceare all leaving; no field lines enter the surface. This is also what we’d expect thefield to look like for a region bounded by a magnetic monopole.
Choice E The field loops in on itself, so the total number of field lines is zero. This fitswith the above law.
Answer: (D)
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Gauss’ Law cxi0.182 Gauss’ Law
To determine an electric field that could exist in a region of space with no charges weturn to Gauss’ Law.
∇ · E = 0 (0.182.1)
or rather∂∂x
Ex +∂∂y
Ey +∂∂z
Ez = 0 (0.182.2)
So we analyze each choice in turn to get our answer.
Choice A
E = 2xyi − xyk
∇ · E =∂∂x
2xy +∂∂z
(−xz)
= 2y + x , 0 (0.182.3)
Choice B
E = −xy j + xzk
∇ · E =∂∂y
(−xy) +∂∂z
xz
= −x + x = 0 (0.182.4)
Choice C
E = xzi + xz j
∇ · E =∂∂x
xz +∂∂y
xz
= z + 0 , 0 (0.182.5)
Choice D
E = xyz(i + j)
∇ · E =∂∂x
xyz +∂∂y
xyz
= yz + xz , 0 (0.182.6)
Choice E
E = xyzi
∇ · E =∂∂x
xyz
= yz , 0 (0.182.7)
Answer: (B)
©2009 David S. Latchman
DRAFT
cxii GR8677 Exam Solutions0.183 Biot-Savart Law
We can determine the magnetic field produced by our outer wire from the Biot-SavartLaw
dB =µ0
4πd` × r
r3 (0.183.1)
As our radius and differential length vectors are orthogonal, the magnetic field worksout to be
dB =µ0
4πId`rr3
=µ0I4π·
rdθr2
B =µ0I4πr
∫ 2π
0dθ
=µ0I2b
(0.183.2)
We know from Faraday’s Law, a changing magnetic flux induces a EMF,
E =dΦ
dt(0.183.3)
where Φ = BA. The magnetic flux becomes
Φ =µ0I2b· πa2 (0.183.4)
The induced EMF becomes
E =µ0π
2
(a2
b
)dIdt
=µ0π
2
(a2
b
)ωI0 sinωt (0.183.5)
Answer: (B)
0.184 Zeeman Effect and the emission spectrum of atomicgases
Another knowledge based question best answered by the process of elimination.
Stern-Gerlach Experiemnt The Stern-Gerlach Experiment has nothing to do withspectral emissions. This experiment, performed by O. Stern and W. Gerlachin 1922 studies the behavior of a beam atoms being split in two as they passthrough a non-uniform magnetic field.
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Spectral Lines in High Density and Low Density Gases cxiiiStark Effect The Stark Effect deals with the shift in spectral lines in the presence of
electrical fields; not in magnetic fields.
Nuclear Magnetic Moments of atoms Close, the splitting seen in the Stern-GerlachExperiment is due to this. Emission spectrum typically deals with electrons andso we would expect it to deal with electrons on some level.
Emission lines are split in two Closer but still not accurate. There is splitting but insome cases it may be more than two.
Emission lines are greater or equal than in the absence of the magnetic field This weknow to be true.
The difference in the emission spectrum of a gas in a magnetic field is due to theZeeman effect.
Answer: (E)
0.185 Spectral Lines in High Density and Low DensityGases
We expect the spectral lines to be broader in a high density gas and narrower in a lowdensity gas ue to the increased colissions between the molecules. Atomic collisionsadd another mechanism to transfer energy.
Answer: (C)
0.186 Term Symbols & Spectroscopic Notation
To determine the term symbol for the sodium ground state, we start with the electronicconfiguration. This is easy as they have given us the number of electrons the elementhas thus allowing us to fill sub-shells using the Pauli Exclusion Principle. We get
1s2, 2s2, 2p6, 3s1 (0.186.1)
We are most interested in the 3s1 sub-shell and can ignore the rest of the filled sub-shells. As we only have one valence electron then ms = +1/2. Now we can calculatethe total spin quantum number, S. As there is only one unpaired electron,
S =12
(0.186.2)
Now we can calculate the total angular momentum quantum number, J = L + S. Asthe 3s sub-shell is half filled then
L = 0 (0.186.3)
©2009 David S. Latchman
DRAFT
cxiv GR8677 Exam SolutionsThis gives us
J =12
(0.186.4)
and as L = 0 then we use the symbol S. Thus our term equation becomes2S 1
2(0.186.5)
Answer: (B)
0.187 Photon Interaction Cross Sections for Pb
Check Brehm p. 789
Answer: (B)
0.188 The Ice Pail Experiment
Gauss’ law is equivalent to Coulomb’s Law because Coulomb’s Law is an inversesquare law; testing one is a valid test of the other. Much of our knowledge of theconsequences of the inverse square law came from the study of gravity. Jason Priestlyknew that there is no gravitational field within a spherically symmetrical mass distri-bution. It was suspected that was the same reason why a charged cork ball inside acharged metallic container isn’t attracted to the walls of a container.
Answer: (E)
0.189 Equipartition of Energy and Diatomic Molecules
To answer this question, we will turn to the equipartition of energy equation
cv =
(f2
)R (0.189.1)
where f is the number of degrees of freedom. In the case of Model I, we see that
Degrees of Freedom Model I Model II
Translational 3 3Rotational 2 2Vibrational 0 2
Total 5 7
Table 0.189.1: Specific Heat, cv for a diatomic molecule
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Fermion and Boson Pressure cxvSo the specific heats for Models I & II are
cvI =52
Nk cvII =72
Nk
Now we can go about choosing our answer
Choice A From our above calculations, we see that cvI = 5/2Nk. So this choice isWRONG.
Choice B Again, our calculations show that the specific heat for Model II is larger thanthan of Model I. This is due to the added degrees of freedom (vibrational) that itpossesses. So this choice is WRONG.
C & D They both contradict the other and they both contradict Choice (E).
E This is TRUE. We know that at higher temperatures we have an additional degreeof freedom between our diatomic molecule.
Answer: (E)
0.190 Fermion and Boson Pressure
To answer this question, we must understand the differences between fermions andbosons. Fermions follow Fermi-Dirac statistics and their behavior is obey the PauliExclusion Principle. Basically, this states that no two fermions may have the samequantum state. Bosons on the other hand follow Bose-Einstein statistics and severalbosons can occupy the same quantum state.
As the temperature of a gas drops, the particles are going to fill up the available energystates. In the case of fermions, as no two fermions can occupy the same state, thenthese particles will try to occupy all the energy states it can until the highest is filled.Bosons on the other hand can occupy the same state, so they will all ‘group’ togetherfor the lowest they can. Classically, we don’t pay attention to this grouping, so basedon our analyis, we expect,
PF > PC > PB (0.190.1)
where PB is the boson pressure, PC is the pressure with no quantum effects taking placeand PF to be the fermion pressure.
Answer: (B)
0.191 Wavefunction of Two Identical Particles
We are given the wavefunction of two identical particles,
ψ =1√
2
[ψα(x1)ψβ(x2) + ψβ(x1)ψα(x2)
](0.191.1)
©2009 David S. Latchman
DRAFT
cxvi GR8677 Exam SolutionsThis is a symmetric function and satisfies the relation
ψαβ(x2, x1) = ψαβ(x1, x2) (0.191.2)
Symmetric functions obey Bose-Einstein statistics and are known as bosons. Uponexamination of our choices, we see that21
electrons fermion
positrons fermion
protons fermion
neutron fermion
deutrons Boson
Incidentally, a anti-symmetric function takes the form,
ψ =1√
2
[ψα(x1)ψβ(x2) − ψβ(x1)ψα(x2)
](0.191.3)
and satisfies the relationψαβ(x2, x1) = −ψαβ(x1, x2) (0.191.4)
These obey Fermi-Dirac Statistics and are known as fermions.
Answer: (E)
0.192 Energy Eigenstates
We may recognize this wavefunction from studying the particle in an infinite wellproblem and see this is the n = 2 wavefunction. We know that
En = n2E0 (0.192.1)
We are given that E2 = 2 eV. So
E0 =1n2 E2
=24
eV
=12
eV (0.192.2)
Answer: (C)21You could have easily played the ‘one of thes things is not like the other...’ game
David S. Latchman ©2009
DRAFT
Bragg’s Law cxvii0.193 Bragg’s Law
We recall Bragg’s Law2d sinθ = nλ (0.193.1)
Plugging in what we know, we determine λ to be
λ = 2(3 Å)(sin 30)
= 2(3 Å)(0.5)
= 3 Å (0.193.2)
We employ the de Broglie relationship between wavelength and momentum
p =hλ
(0.193.3)
We get
mv =hλ
⇒ v =h
mλ
=6.63 × 10−34
(9.11 × 10−31)(3 × 10( − 10))(0.193.4)
We can determine the order of our answer by looking at the relevant indices
− 34 − (−31) − (−10) = 7 (0.193.5)
We see that (D) is close to what we are looking for.
Answer: (D)
0.194 Selection Rules for Electronic Transitions
The selection rules for an electric dipole transition are
∆` = ±1 Orbital angular momentum∆m` = 0,±1 Magnetic quantum number∆ms = 0 Secondary spin quantum number,∆ j = 0,±1 Total angular momentum
We have no selection rules for spin, ∆s, so we can eliminate this choice.
Answer: (D)
©2009 David S. Latchman
DRAFT
cxviii GR8677 Exam Solutions0.195 Moving Belt Sander on a Rough Plane
We know the work done on a body by a force is
W = F × x (0.195.1)
We can relate this to the power of the sander; power is the rate at which work is done.So
P =dWdt
= Fdxdt
= Fv (0.195.2)
The power of the sander can be calculated
P = VI (0.195.3)
where V and I are the voltage across and the current through the sander. By equatingthe Mechanical Power, eq. (0.195.2) and the Electrical Power, eq. (0.195.3), we candetermine the force that the motor exerts on the belt.
F =VIv
=120 × 9
10= 108 N (0.195.4)
The sander is motionless, soF − µR = 0 (0.195.5)
where R is the normal force of the sander pushing against the wood. Thus the coefficientof friction is
µ =FR
=108100
= 1.08 (0.195.6)
Answer: (D)
0.196 RL Circuits
When the switch, S, is closed, a magnetic field builds up within the inductor and theinductor stores energy. The charging of the inductor can be derived from Kirchoff’sRules.
E − IR − LdIdt
= 0 (0.196.1)
and the solution to this is
I(t) = I0
[1 − exp
(R1tL
)](0.196.2)
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DRAFT
RL Circuits cxixwhere the time constant, τ1 = L/R1.
We can find the voltage across the resistor, R1, by multiplying the above by R1, givingus
V(t) = R1 · I0
[1 − exp
(R1tL
)]= E
[1 − exp
(R1tL
)](0.196.3)
The potential at A can be found by measuring the voltage across the inductor. Giventhat
E − VR1 − VL = 0∴ VL = E − VR1
= E exp(R1t
L
)(0.196.4)
This we know to be an exponential decay and (fortunately) limits our choices to either(A) or (B)22
The story doesn’t end here. If the inductor was not present, the voltage would quicklydrop and level off to zero but with the inductor present, a change in current means achange in magnetic flux; the inductor opposes this change. We would expect to see areversal in the potential at A. Since both (A) and (B) show this flip, we need to thinksome more.
The energy stored by the inductor is
UL =12
LI20 =
12
L(E
R1
)2
(0.196.5)
With S opened, the inductor is going to dump its energy across R2 and assuming thatthe diode has negligible resistance, all of this energy goes to R2. Thus
U =12
L(
VR2
R2
)2
(0.196.6)
The above two equations are equal, thus
E
R1=
VR2
R2
VR2 = 3E (0.196.7)
We expect the potential at A to be larger when S is opened. Graph (B) fits this choice.
Answer: B22If you get stuck beyond this point, you can guess. The odds are now in your favor.
©2009 David S. Latchman
DRAFT
cxx GR8677 Exam Solutions0.197 Carnot Cycles
The Carnot Cycle is made up of two isothermal transformations, KL and MN, and twoadiabatic transformations, LM and NK. For isothermal transformations, we have
PV = nRT = a constant (0.197.1)
For adiabatic transformations, we have
PVγ = a constant (0.197.2)
where γ = CP/CV.
For the KL transformation, dU = 0.
Q2 = WK→L
∴WK→L =
∫ VL
VK
PdV
= nRT2 ln(VK
VL
)(0.197.3)
For the LM transformation,PLVγ
L = PMVγM (0.197.4)
For the MN transformation, dU = 0.
Q1 = WM→N
∴WM→N =
∫ VN
VM
PdV
= nRT1 ln(VN
VM
)(0.197.5)
For the NK transformation,PNVγ
N = PKVγK (0.197.6)
Dividing eq. (0.197.4) and eq. (0.197.6), gives
PLVγL
PKVγK
=PMVγ
M
PNVγN
∴VL
VK=
VM
VN(0.197.7)
The effeciency of an engine is defined
η = 1 −Q1
Q2(0.197.8)
David S. Latchman ©2009
DRAFT
Carnot Cycles cxxiWe get
η = 1 −Q1
Q2= 1 −
−WM→N
WK→L
= 1 −nRT1 ln
(VMVN
)nRT2 ln
(VKVL
)= 1 −
T1
T2(0.197.9)
1. We see that
1 −Q1
Q2= 1 −
T1
T2
∴Q1
Q2=
T1
T2(0.197.10)
Thus choice (A) is true.
2. Heat moves from the hot reservoir and is converted to work and heat. Thus
Q2 = Q1 + W (0.197.11)
The entropy change from the hot reservoir
S =dQ2
T(0.197.12)
As the hot reservoir looses heat, the entropy decreases. Thus choice (B) is true.
3. For a reversible cycle, there is no net heat flow over the cycle. The change inentropy is defined by Calusius’s Theorem.∮
dQT
= 0 (0.197.13)
We see that the entropy of the system remains the same. Thus choice (C) is false.
4. The efficieny is defined
η =WQ2
(0.197.14)
This becomes
η = 1 −Q1
Q2
=Q2 −Q1
Q2(0.197.15)
Thus W = Q2 −Q1. So choice (D) is true,
5. The effeciency is based on an ideal gas and has no relation to the substance used.So choice (E) is also true.
Answer: (C)
©2009 David S. Latchman
DRAFT
cxxii GR8677 Exam Solutions0.198 First Order Perturbation Theory
Perturbation Theory is a procedure for obtaining approximate solutions for a perturbedstate by studying the solutions of the unperturbed state. We can, and shouldn’t,calculate this in the exam.
We can get the first order correction to be ebergy eigenvalue
E1n = 〈ψ0
n|H′
|ψ0n〉 (0.198.1)
From there we can get the first order correction to the wave function
ψ1n =
∑m,n
〈ψ0m|H
′
|ψ0n〉(
E0n − E0
m) (0.198.2)
and can be expressed asψ1
n =∑m,n
c(n)m ψ
0m (0.198.3)
you may recognize this as a Fourier Series and this will help you knowing that theperturbing potential is one period of a saw tooth wave. And you may recall that theFourier Series of a saw tooth wave form is made up of even harmonics.
Answer: (B)23
0.199 Colliding Discs and the Conservation of AngularMomentum
As the disk moves, it possessed both angular and linear momentums. We can notexactly add these two as they, though similar, are quite different beasts. But we candefine a linear angular motion with respect to some origin. As the two discs hit eachother, they fuse. This slows the oncoming disc. We can calculate the linear angularmomentum
L = r × p (0.199.1)
where p is the linear momentum and r is the distance from the point P to the center ofdisc I. This becomes
Lv0 = MR × v0
= −MRv0 (0.199.2)
It’s negative as the cross product of R and v0 is negative.
The Rotational Angular Momentum is
Lω0 = Iω0 (0.199.3)
23Griffiths gives a similar problem in his text
David S. Latchman ©2009
DRAFT
Electrical Potential of a Long Thin Rod cxxiiiAdding eq. (0.199.3) and eq. (0.199.2) gives the total angular momentum.
L = Lω0 + Lv0
= Iω0 −MRv0
=12
MR2ω0 −12
MR2ω0
= 0
Thus the total angular momentum at the point P is zero.
Answer: (A)
0.200 Electrical Potential of a Long Thin Rod
We have charge uniformly distributed along the glass rod. It’s linear charge density is
λ =Q`
=dQdx
(0.200.1)
The Electric Potential is defined
V(x) =q
4πε0x(0.200.2)
We can ‘slice’ our rod into infinitesimal slices and sum them to get the potential of therod.
dV =1
4πε0
λdxx
(0.200.3)
We assume that the potential at the end of the rod, x = ` is V = 0 and at some pointaway from the rod, x, the potential is V. So∫ V
0dV =
λ4πε0
∫ x
`
dxx
=λ
4πε0ln
(x`
)(0.200.4)
Where x = 2`, eq. (0.200.4) becomes
V =Q`
14πε0
ln(2``
)=
Q`
14πε0
ln 2 (0.200.5)
Answer: (D)
©2009 David S. Latchman
DRAFT
cxxiv GR8677 Exam Solutions0.201 Ground State of a Positronium Atom
Positronium consists of an electron and a positron bound together to form an “exotic”atom. As the masses of the electron and positron are the same, we must use a reduced-mass correction factor to determine the enrgy levels of this system.24. The reducedmass of the system is
1µ
=1
me+
1mp
(0.201.1)
Thus /mu is
µ =me ·mp
me + mp
=me
2(0.201.2)
The ground state of the Hydrogen atom, in terms of the reduced mass is
E1 = −µ
meE0
= −12
E0 (0.201.3)
where E0 = 13.6 eV.
Answer: (B)
0.202 The Pinhole Camera
A pinhole camera is simply a camera with no lens and a very small aperature. Lightpasses through this hole to produce an inverted image on a screen. For the photographybuffs among you, you know that by varying the size of a camera’s aperature canaccomplish various things; making the aperature bigger allows more light to enter andproduces a “brighter” picture while making the aperature smaller produces a sharperimage.
In the case of the pinhole camera, making the pinhole, or aperature, smaller producesa sharper image because it reduces “image overlap”. Think of a large hole as a set oftiny pinholes places close to each other. This results in an infinite amount of imagesoverlapping each other and hence a blurry image. So to produce a sharp image, itis best to use the smallest pinhole possible, the tradeoff being an image that’s not as“bright”.
There are limits to the size of our pinhole. We can not say, for example, use an infinitelysmall pinhole the produce the sharpest possible image. Beyond some point diffractioneffects take place and will ruin our image.
24Place cite here
David S. Latchman ©2009
DRAFT
The Pinhole Camera cxxvConsider a pinhole camera of length, D, with a pinhole of diameter, d. We know howmuch a beam of light will be diffracted through this pinhole by25
d sinθ = mλ (0.202.1)
this is the equation for the diffraction of a single slit. As θ is small and we will considerfirst order diffraction effects, eq. (0.202.1) becomes
dθ = λ
⇒ θ =λd
(0.202.2)
The “size” of this spread out image is
y = 2θD
=2λD
d(0.202.3)
So the ‘blur’ of our resulting image is
B = y − d
=2λD
d− d (0.202.4)
We can see that we want to reduce y as much as possible. i.e. make it d. So eq. (0.202.4)becomes
0 =2λD
d− d
∴2λD
d= d
Thus d =√
2λD (0.202.5)
So we’d want a pinhole of that size to produce or sharpest image possible. This resultis close to the result that Lord Rayleigh used, which worked out to be
d = 1.9√
Dλ (0.202.6)
Answer: (A)
25Add image of pinhole camera
©2009 David S. Latchman
DRAFT
cxxvi GR8677 Exam Solutions
David S. Latchman ©2009
DRAFTConstants & Important Equations
.1 Constants
Constant Symbol ValueSpeed of light in a vacuum c 2.99 × 108 m/sGravitational Constant G 6.67 × 10−11 m3/kg.s2
Rest Mass of the electron me 9.11 × 10−31 kgAvogadro’s Number NA 6.02 × 1023 mol-1
Universal Gas Constant R 8.31 J/mol.KBoltzmann’s Constant k 1.38 × 10−23 J/KElectron charge e 1.60 × 10−9CPermitivitty of Free Space ε0 8.85 × 10−12 C2/N.m2
Permeability of Free Space µ0 4π × 10−7 T.m/AAthmospheric Pressure 1 atm 1.0 × 105 M/m2
Bohr Radius a0 0.529 × 10−10 m
Table .1.1: Something
.2 Vector Identities
.2.1 Triple Products
A · (B × C) = B · (C ×A) = C · (A × B) (.2.1)A × (B × C) = B (A · C) − C (A · B) (.2.2)
DRAFT
cxxviii Constants & Important Equations.2.2 Product Rules
∇(
f g)
= f(∇g
)+ g
(∇ f
)(.2.3)
∇ (A · B) = A × (∇ × B) + B × (∇ ×A) + (A · ∇) B + (B · ∇) A (.2.4)∇ ·
(f A
)= f (∇ ·A) + A ·
(∇ f
)(.2.5)
∇ · (A × B) = B · (∇ ×A) −A · (∇ × B) (.2.6)∇ ×
(f A
)= f (∇ ×A) −A ×
(∇ f
)(.2.7)
∇ × (A × B) = (B · ∇) A − (A · ∇) B + A (∇ · B) − B (∇ ·A) (.2.8)
.2.3 Second Derivatives
∇ · (∇ ×A) = 0 (.2.9)∇ ×
(∇ f
)= 0 (.2.10)
∇ × (∇ ×A) = ∇ (∇ ·A) − ∇2A (.2.11)
.3 Commutators
.3.1 Lie-algebra Relations
[A,A] = 0 (.3.1)[A,B] = −[B,A] (.3.2)[A, [B,C]] + [B, [C,A]] + [C, [A,B]] = 0 (.3.3)
.3.2 Canonical Commutator
[x, p] = i~ (.3.4)
.3.3 Kronecker Delta Function
δmn =
0 if m , n;1 if m = n;
For a wave function ∫ψm(x)∗ψn(x)dx = δmn (.3.5)
David S. Latchman ©2009
DRAFT
Linear Algebra cxxix.4 Linear Algebra
.4.1 Vectors
Vector Addition
The sum of two vectors is another vector
|α〉 + |β〉 = |γ〉 (.4.1)
Commutative|α〉 + |β〉 = |β〉 + |α〉 (.4.2)
Associative|α〉 +
(|β〉 + |γ〉
)=
(|α〉 + |β〉
)+ |γ〉 (.4.3)
Zero Vector|α〉 + |0〉 = |α〉 (.4.4)
Inverse Vector|α〉 + | − α〉 = |0〉 (.4.5)
©2009 David S. Latchman
DRAFT
cxxx Constants & Important Equations
David S. Latchman ©2009
DRAFTBibliography
[1] John J. Brehm and William J. Mullin. Introduction to the Structure of Matter, chapter11-6, pages 567–571. Wiley, first edition, 1989.
[2] David J. Griffiths. Introduction to Electrodyanmics, chapter 3.2.1, pages 121–123.Prentice Hall, third edition, 1999.
[3] Douglas Adams. The restaurant at the end of the universe.
[4] Wikipedia. Spectral line — wikipedia, the free encyclopedia, 2009. [Online;accessed 17-March-2009].
[5] Wikipedia. Term symbol — wikipedia, the free encyclopedia, 2008. [Online;accessed 22-March-2009].
[6] John J. Brehm and William J. Mullin. Introduction to the Structure of Matter, chapter5-10, pages 283–287. Wiley, first edition, 1989.
[7] John J. Brehm and William J. Mullin. Introduction to the Structure of Matter, chapter11-1, pages 539–540. Wiley, first edition, 1989.
[8] David J. Griffiths. Introduction to Quantum Mechanics, chapter 5.1.1, pages 203–205.Prentice Hall, second edition, 2005.
[9] David J. Griffiths. Introduction to Quantum Mechanics, chapter 9.3.3, pages 359–362.Prentice Hall, second edition, 2005.
[10] David J. Griffiths. Introduction to Quantum Mechanics, chapter 6.1.1, page 249.Prentice Hall, second edition, 2005.
[11] David J. Griffiths. Introduction to Quantum Mechanics, chapter 6.1.2, pages 251–254.Prentice Hall, second edition, 2005.
[12] David J. Griffiths. Introduction to Quantum Mechanics, chapter 6.1.2, page 254.Prentice Hall, second edition, 2005.
DRAFTIndex
AmplifiersGR8677 Q39, xci
Angular Momentum, see Rotational Mo-tion
Binding EnergyGR8677 Q41, xcii
Bohr ModelGR8677 Q19, lxxxiiHydrogen Model, lv
Celestial Mechanics, xxivCircular Orbits, xxvEscape Speed, xxivKepler’s Laws, xxvNewton’s Law of Gravitation, xxivOrbits, xxvPotential Energy, xxiv
Cetripetal MotionGR8677 Q06, lxxvi
Circular Orbits, see Celestial MechanicsCommutators, cxxviii
Canonical Commutators, cxxviiiKronecker Delta Function, cxxviiiLie-algebra Relations, cxxviii
Compton Effect, lviiiCompton Wavelength
GR8677 Q45, xcivConductivity
GR8677 Q23, lxxxivCounting Statistics, lxxi
GR8677 Q40, xciCurrent Density
GR8677 Q09, lxxvii
DielectricsGR8677 Q03, lxxiv
Digital CircuitsGR8677 Q38, xci
Doppler Effect, xxiiDrag Force
GR8677 Q01, lxxiii
Elastic ColissionsGR8677 Q05, lxxv
ElectricityGR8677 Q24, lxxxv
Electron SpinGR8677 Q27, lxxxvi
Electronic ConfigurationGR8677 Q30, lxxxviii
Fleming’s Right Hand RuleGR8677 Q29, lxxxviii
Franck-Hertz Experiment, lxiGR8677 Q47, xcv
Gauss’ LawGR8677 Q10, lxxviii
Gravitation, see Celestial Mechanics
Hall EffectGR8677 Q50, xcvi
HamiltonianGR8677 Q35, xc
InterferenceGR8677 Q13, lxxix
Kepler’s Laws, see Celestial MechanicsKronecker Delta Function, cxxviii
Laboratory MethodsGR8677 Q40, xci
Linear Algebra, cxxix
DRAFT
Index cxxxiiiVectors, cxxix
Lorentz Force LawGR8677 Q25, lxxxv
Lorentz TransformationGR8677 Q22, lxxxiv
Maximum Power TheoremGR8677 Q64, ciii
Maxwell’s LawsGR8677 Q11, lxxix
MechanicsGR8677 Q07, lxxviGR8677 Q08, lxxviiGR8677 Q37, xc
Moment of Inertia, see Rotational Motion
Newton’s Law of Gravitation, see CelestialMechanics
Nuclear PhysicsRadioactive Decay
GR8677 Q17, lxxxi
Oscillatory Motion, xviiiCoupled Harmonic Oscillators, xx
GR8677 Q43, xciiDamped Motion, xixKinetic Energy, xviiiPotential Energy, xixSimple Harmonic Motion Equation, xviiiSmall Oscillations, xixTotal Energy, xviii
Parallel Axis Theorem, see Rotational Mo-tion
Particle PhysicsMuon
GR8677 Q16, lxxxiPhotoelectric Effect
GR8677 Q31, lxxxixGR8677 Q32, lxxxixGR8677 Q33, lxxxix
Potential EnergyGR8677 Q34, lxxxix
Principle of Least ActionGR8677 Q36, xc
ProbabilityGR8677 Q15, lxxx
Rolling Kinetic Energy, see Rotational Mo-tion
Rotational Kinetic Energy, see RotationalMotion
Rotational Motion, xxiiAngular Momentum, xxiiiMoment of Inertia, xxiiParallel Axis Theorem, xxiiiRolling Kinetic Energy, xxiiiRotational Kinetic Energy, xxiiTorque, xxiii
Satellite OrbitsGR8677 Q02, lxxiv
Schrodinger’s EquationGR8677 Q18, lxxxii
Space-Time IntervalGR8677 Q21, lxxxiii
Special RelativityDoppler Shift
GR8677 Q12, lxxixEnergy
GR8677 Q20, lxxxiiiSpecific Heat
GR8677 Q14, lxxixStefan-Boltzmann’s Equation
GR8677 Q46, xcivSubject, xlivSystem of Particles, xxiv
Thin Film InterferenceGR8677 Q73, cvii
Torque, see Rotational Motion
Vector Identities, cxxviiProduct Rules, cxxviiiSecond Derivatives, cxxviiiTriple Products, cxxvii
Wave EquationGR8677 Q04, lxxiv
Wave functionGR8677 Q28, lxxxvii
X-RaysGR8677 Q26, lxxxv
©2009 David S. Latchman