Physics Chapter 10
Physics Chapter 10Nuclear PhysicsBy:J. Rowe Planetary Model
Electron Cloud Model
A semi-accurate depiction of the helium atom. In the nucleus,
the protons are in red and neutrons are in purple. In reality, the
nucleus is also spherically symmetrical.2Basic ConceptsThere are 3
different types of particles we find within the atom.These are
known as the Proton, the Neutron, and the Electron.
ProtonNeutronElectronSize1
amu1amuNegligibleMass1.67x10-271.67x10-279.11x10-31Charge+1e--1ee,
or elementary charge, is the basic charge used by the particles of
the atom. Elementary charge is always 1.60x10-19 C.3Basic Concepts
Cont.The Proton and the Neutron are found in the nucleus of the
atom.Whereas the Electron is found outside the nucleus of the atom,
it circulates around the nucleus either as the Planetary model of
the atom or as the Quantum Mechanical model of the atom.The Quantum
Mechanical model of the atom, or the electron cloud, is a more
recent finding on the structure of an atom. It shows that electrons
do not circulate around the nucleus in a planetary fashion, but
instead they follow their own orbitals, and it is next to
impossible to locate the exact location of an electron except for
knowing the orbital that the electron circulates on.
Plancks Photon: PrefaceDuring the time of Einstein and other
scientists were well on their way of discovering the different
properties of light, two well known theories, both backed by
scientific evidence, were accepted as answers to what light could
be constructed from.The first theory was the particle theory.This
entailed that light was an array of particles made from tiny,
massless particles called photons. It was this theory that was
backed by Albert Einstein.The second theory was the wave theory of
light.This theory was brought about by Christiaan Huygens and
suggested that light was in fact, a wave. This was further backed
by Thomas Youngs famous Double-Slit experiment.In the end, the two
theorys were equal, but was light a particle, or a wave?Plancks
Photon: Preface Cont.The answer, is both.In the 1920s, Louis De
Broglie had hypothesized that any quantum particle, whether it be
an electron, or a photon, exhibits both particle like and wave like
properties.The reason was because of the way we interact with the
particles themselves.When the Compton effect was done, we could see
that light was obviously a wave.However when the Double-Slit
experiment was completed, we could evidently see that light was a
wave instead of a particle.Wave-Particle Duality was formed when Do
Broglie realized that both could be used in conjunction with one
another to explain that light in fact reacts to the way we test it.
It was Albert Einstein who would be able to back De Broglies
findings.Plancks PhotonAfter that, Planck was able to put his own
constant (h = 6.63 x 10-34 ) That was used to equalize both ends of
the equation.Because of Planck, Einstein, and De Broglie, we are
now able to calculate the frequency, energy, and wavelength of a
photon.Under the photon theory of light, a photon is a bundle of
electromagnetic energy. Photons are always in motion and have a
constant speed of light to all observers, at the speed of light.The
formula for speed of light is c = 2.998 x 108 m/s.
Plancks PhotonWe now know that Albert Einstein, had used De
Broglies findings to spearhead the particle wave duality.The reason
that Einstein had agreed with the link between particles and waves
was because of Max Planck.Planck had been tackling the problem of
blackbody radiation (not important). In order to do so, he had
decided to quantise energy. He called it photons.He had theorized
that photons had different amounts of energy, and that the
frequency of the photons (remember particle wave duality) was
proportional to each other.This can be read as (The energy of a
photon is equal to the frequency of a photon as well.Binding
EnergyWhen doing the electricity unit, we found that like charges
would repel each other, and that opposite charges would attract
each other.Lets think about the atom. We know that the positive
protons are all centered in the nucleus, whereas all the negative
electrons are scattered in a cloud out side the nucleus.Has it ever
occurred to you as to why the protons dont repel away from each
other, and why the electrons dont just stick to the nucleus
instead?Binding Energy Cont.The answer is known as the Strong
Nuclear Force.The Strong Nuclear Force is a fundamental for of
nature that exists between Neutrons that stops that from them from
separating due to the opposing forces that exist protons.Mass and
energy are proportional and equal to each other.There is always an
equal amount of mass and energy in the universe. But they are
always converting to each other.For example, an atoms weight is 1
but if you were to take apart the atom it would weigh more. This is
because when the particles are put together, energy is used to
combine them and it is converted. Mass is converted to energy to
hold the atom together.RadioactivitySometimes, in unstable isotopes
of atoms, the Strong Nuclear Force is unstable, the result, is
small bits and pieces of energy are converted to mass and are
ejected from an atom. There are 2 different types of decay we need
to know about.Nuclear Reactions are reactions that happen within
the atom, for example, Alpha decay could be considered a nuclear
reaction.Essentially a nuclear reaction is when atoms add together
to form bigger atom (fusion)Or they break onto two smaller atoms
(fission)
Alpha DecayAlpha decay can most simply be described like this:1)
The nucleus of an atom splits into two parts.2) One of these parts
(the alpha particle) goes zooming off into space.3) The nucleus
left behind has its atomic number reduced by 2 and its mass number
reduced by 4 (that is, by 2 protons and 2 neutrons).
Beta DecayBeta decay is somewhat more complex than alpha decay
is. These points present a simplified view of what beta decay
actually is:1) A neutron inside the nucleus of an atom breaks down,
changing into a proton.2) It emits an electron and an anti-neutrino
which go zooming off into space.3) The atomic number goes UP by one
and mass number remains unchanged.Are all these processes &
particles related ???Is the atom really the smallest functional
aspect of matter ?? Is there anything smaller than the proton &
neutron or electron ?What makes up a proton or neutron ?Are there
other particles besides PEN, photons & neutrinos ?Particles of
Matter :1 - Elementary / Fundamental Particle the smallest
indivisible portion of matter a.k.a. not made up of any other
functional substance a.k.a. They have no measurable internal
structure. There are 17 types of fundamental particles e.g. quarks,
gluons, photons, gravitons etc
These are the fundamental objects of The Quantum Field Theory
and are divided up in many families and sub-families. Elementary
Particles are grouped based on their spin: Fermions have integer
spins while Bosons have full integer spins
There are 2 types: Elementary Particles & Composite Particle
15What is Integer Spin ??All particles have an intrinsic angular
momentum, as if they were little spinning balls of energySince we
are talking about sub-atomic particles, we refer to sub-atomic
energy as Quantum Energy. The basic Quantum Energy in a spinning
particle can be calculated using the formula E = h, with E =
energy, h = Plancks constant & , = angular velocity or
frequency If an object spin has enough energy to = 0,1 etc full
integer increase/decrease in Planks constant, it has full integer
spinIf an objects spin is only a fractional increase / decrease in
Plancks constant, it has a integer spinPlancks constant, is h =
6.627 10-34 m2 kg / s
Planck discovered that any physical action could not take on an
arbitrary value. Instead, the action must be some multiple of a
very small quantity (later to be named the "quantum of action" and
now called Planck constant). 16
Elementary Particles
Fermions Fermions have mass and are the building blocks of
matterNamed after Enrico Fermi & have a spin number of - or
There are 12 types & each type is called a flavorFermions are
divided into 2 groups based on their interaction with the Strong
Binding Force. Quarks: up, down, strange, charm, bottom, top.
Quarks come in three pairs, called "generations." One member of
each pair has a charge of . The other member has charge -.Leptons:
electron, muon, tau, electron neutrino, mu neutrino, tau neutrino.
The neutrinos have charge 0, hence the neutr- prefix. The other
leptons have charge -1. Each neutrino is named after its
corresponding original lepton: the electron, muon, and tauon.
Quarks interact based on the strong binding force Leptons do not
interact based on the Strong Binding force but instead use the
other 3 fundamental forces 19
Elementary Particles Bosonsbosons are mass-less and behave as
force carriers for fermion interactionsBosons all have full integer
spins. Bosons include: photons and gluons, higgs boson, graviton, Z
& W bosons Photons mediate electromagnetic radiation, Higgs
Boson mediates mass transfer between elementsZ & W Bosons
mediate nuclear radiation energy transfer Gravitons mediate the
gravitational forces
Each type of elementary particle is able to interact with matter
based on the 4 fundamental forces: gravitational, electromagnetic,
strong nuclear, and weak nuclear.232 Composite Particle or Hadron
is formed from a group of elementary particles. Composite or group
particle can be formed from fermions (called baryons) or from
bosons (called mesons)Composite fermions, in which case they are
called baryons.Composite bosons, in which case they are called
mesons.
Baryons (3 types)Nucleons are the fermionic constituents of
normal atomic nuclei: Protons, composed of two up and one down
quark (uud)Neutrons, composed of two down and one up quark
(ddu)
Particles of Matter : There are 2 types: Elementary Particles
& Composite Particle Examples of mesons include the pion, kaon,
and the J/. 24Composite Atomic Nuclear Structure
The Nucleus The Neutron The Proton Nucleus contains Protons
& Neutrons. Protons have UUD while Neutrons have DDU in terms
of quark structure giving protons a (+2/3, +2/3, -1/3) = +1 charge
and neutrons have (-1/3, -1/3 , +2/3) = 0 charge25How do these
Particles behave ?The Standard Model is the most accepted way to
explain how particles behave, and the forces that affect them.
According to this model, the elementary particles are further
grouped into quarks, leptons, and gauge bosons, with the Higgs
boson having a special status The Standard Model to the rescue
!!!Summary
The End . Right ??
