12 TH STANDARD PHYSICS Prepared by: R.RAJENDRAN, M.A., M.Sc., M.Ed., N.INGARAN, M.Sc., M.Phil.,M.Ed., ATOMIC PHYSICS

12TH STANDARDPHYSICS

Prepared by:R.RAJENDRAN, M.A., M.Sc., M.Ed.,N.INGARAN, M.Sc., M.Phil.,M.Ed.,

ATOMIC PHYSICS

1. At atmospheric pressure, air and other gases

are …………… conductors of electricity.

a) good

b) semi

c) poor

d) rich

CHOOSE THE CORRECT ANSWER

2. Electric current may be passed through a gas

by allowing ……………. to pass through them.

a) light

b) infra-red

c) X –rays

d) none of the above


3. Electrons were discovered by ………………

a) Millikan

b) Goldstein

c) Einstein

d) Thomson


4. …………………… is an arrangement to study the

conduction of electricity through gases.

a) X-ray tube

b) Coolidge tube

c) discharge tube

d) GM counter


5. In a discharge tube, the potential difference

applied between the two electrodes is

………………

a) 10000 V

b) 20000 V

c) 60000 V

d) 50000 V


6. In a discharge tube, the discharge of electricity

through gases starts at a pressure of about …..

a) 100 mm of Hg

b) 1 mm of Hg

c) 10 mm of Hg

d) 0.01 mm of Hg


7. In a discharge tube, the positive column is

produced at a pressure of about ………………

a) 100 mm of Hg

b) 1 mm of Hg

c) 10 mm of Hg

d) 0.01 mm of Hg


8. In a discharge tube, Crooke’s dark space is

produced at a pressure of about ……………

a) 100 mm of Hg

b) 1 mm of Hg

c) 10 mm of Hg

d) 0.01 mm of Hg


9. Cathode rays travel with a velocity up to

………………. of the velocity of light.

a) (1 /100)th

b) (1 /10)th

c) (1 /1000)th

d) (1 /10000)th


10. Canal rays were discovered by ……………….in

the year 1886.

a) Millikan

b) Goldstein

c) Einstein

d) Thomson


11. In 1887, ………………… measured the specific

charge of the cathode ray particles.

a) Millikan

b) Goldstein

c) Einstein

d) Thomson


12. If V is the potential difference between the

two plates and d is the distance between

them, then E = …

a) V d

b) d / V

c) V / d

d) V2 / d


13. e / m value of the electron is …………………..

a) 1.7592 X 1011 C kg-1

b) 1.7592 X 1011 C kg

c) 1.602 X 1019 C kg-1

d) 1.602 X 10-19 C kg-1


14. Millikan’s experiment is used for the

measurement of ………… of the electron.

a) density

b) specific charge

c) mass

d) charge


15. In Millikan’s experiment, the potential

difference applied between the two electrodes

is ………

a) 10000 V

b) 20000 V

c) 60000 V

d) 50000 V


16. The net downward force acting on the oil

drop = ……………..

a) zero

b) maximum

c) minimum

d) ⅓ X 4 π a3 ( ρ - ζ ) g



17. In Millikan’s experiment, the charge of the

electron q = ……………

a) ⅓ X 4 π a3 ( ρ - ζ ) g

b) 4 π a3 ( ρ - ζ ) g

c) (⅓ )π a3 ( ρ - ζ ) g

d) zero

18. In Millikan’s experiment, the charge value of

the electron = ………………….

a) 1.7592 X 1011 C kg-1

b) 1.7592 X 1011 C kg

c) 1.602 X 1019 C kg-1

d) 1.602 X 10-19 C kg-1


19. The concept of atoms was proposed by ……………

a) Bohr

b) Thomson

c) Dalton

d) Prout


20. Prout suggested that all elements are made

up of atoms of …………………

a) carbon

b) helium

c) hydrogen

d) nitrogen


21. Atom is a sphere of positive charge in which

the electrons are embedded. This was

suggested by ..…

a) Bohr

b) Thomson

c) Dalton

d) Prout


22. In the case of hydrogen atom, Thomson’s

model gives only one spectral line of about

……………

a) 3300 Ao

b) 2300 Ao

c) 1300 Ao

d) 4300 Ao


23. The scattering of α particles provide useful

information about the structure of the

………………..

a) atom

b) hydrogen

c) CO2

d) oxygen


24. The diameter of the atom is about …………..

a) 10-20 m

b) 10-10 m

c) 10-14 m

d) 1010 m


25. The diameter of the nucleus is about

…………….

a) 10-20 m

b) 10-10 m

c) 10-14 m

d) 1010 m


26. According to electromagnetic theory, an

accelerated electric charge must radiate

energy in the form of ……

a) light

b) infra-red rays

c) X –rays

d) electromagnetic waves


27. An electron revolving in the stationary orbit

does not radiate ………...

a) lepton

b) energy

c) meson

d) particle


28. According to Bohr’s quantization condition,

the angular momentum of the electron =

……………

a) h / 2

b) 2 π / n h

c) nh / 2π

d) 2π nh


29. The radius of the nth orbit of the electron is

proportional to the square of the ………

quantum number

a) spin

b) principal

c) magnetic

d) angular momentum


30. Bohr radius value r1 = …………………

a) 0.63 Ao

b) 0.83 Ao

c) 0.53 Ao

d) 0.43 Ao


31. The energy of the electron En = ……………..

a) - z2me4 / 8ε02n2h2

b) z2me4 / 8ε02n2h2

c) n2h2ε0 / π mze2

d) - z2me4 / 4ε02n2h2


32. 1 electron volt = ……………… J

a) 1.602 X 1019

b) 1.602 X 10-19

c) 9.11 X 10-31

d) 9.11 X 1031


33. Rydberg’s constant value R = ……………….

a) 1.094 X 107 m-1

b) 1.602 X 109

c) 1.602 X 10-19

d) 9.11 X 10-31


34. The spectral lines of Lyman series of

hydrogen atom lie in the ………… region.

a) UV

b) Visible

c) infra - red

d) gamma


35. The spectral lines of Balmer series of

hydrogen atom lie in the ……………..

a) UV

b) Visible

c) infra - red

d) gamma


36. The spectral lines of Paschen series of

hydrogen atom lie in the ……………….

a) UV

b) Visible

c) infra - red

d) gamma


37. The spectral lines of Brakett series of

hydrogen atom lie in the ………………

a) UV

b) Visible

c) infra - red

d) gamma


38. The spectral lines of Pfund series of hydrogen

atom lie in the …………..

a) UV

b) Visible

c) infra - red

d) gamma


39. The wavelengths of D1 and D2 lines of

sodium are .................

a) 5809Ao ,5896 Ao

b) 5986Ao ,5980 Ao

c) 5689Ao ,5690 Ao

d) 5896Ao ,5890 Ao


40. The energy required to raise an atom from its

normal state into an excited state is called …….

energy.

a) excitation potential

b) potential

c) kinetic

d) stellar


41. The value of ionization potential energy for

hydrogen atom is …………

a) 13.6 eV

b) 30.6 eV

c) 3.4 eV

d) 10.2 eV


42. The fine structure of spectral lines can not be

explained by ………… theory.

a) Raman

b) Newton

c) Bohr

d) Huygens


43. It is found that when magnetic field is applied

to the atom, each of the spectral line is split into

several lines. This effect is called ……… effect.

a) Stark

b) Zeeman

c) Raman

d) Tyndal


44. According to Somerfield's atom model, for any

principal quantum number n, there are n possible

sub-shells, out of which one is circular and the

remaining two are ……………. in shape.

a) elliptical

c) semi-circular

c) square

d) rectangle


45. X-rays were discovered by ……………

a) Raman

b) Newton

c) Roentgen

d) Huygens


46. X-rays are electromagnetic waves of short

wavelength in the range of ……………

a) 0.5 Ao to 10 Ao

b) 0.5 Ao to 100 Ao

c) 0.5 Ao to 1000 Ao

d) 10 Ao to 100 Ao


47. Roentgen was awarded Nobel prize in 1901

for the discovery of …………….

a) gamma

b) UV

c) beta

d) X-rays


48. When fast moving electrons are suddenly

stopped by a metallic target, ……… are

produced.

a) gamma rays

b) UV rays

c) X-rays

d) beta rays


49. In Coolidge tube, a high potential of about

…………… is applied between filament F and the

target T.

a) 10000 V

b) 20000 V

c) 60000 V

d) 50000 V


50. X-rays are of ……………. types.

a) 3

b) 4

c) 2

d) 5


51. X-rays having wavelength of 4Ao or above are

called ………………

a) hard X –rays

b) soft X – rays

c) medium X – rays

d) gamma rays


52. X-rays having low wavelength in the order of 1Ao

are called ……………

a) hard X –rays

b) soft X – rays

c) medium X – rays

d) gamma rays


53. The penetrating power of hard X-rays is …………….

a) low

b) very low

c) high

d) zero


54. When X-rays fall on certain metals, they liberate

…………………

a) protons

b) photons

c) electrons

d) mesons


55. To detect and measure the intensity of the X-

rays, ………………. chamber is used.

a) Thomson

b) Bohr

c) ionization

d) Dalton


56. Any plane containing an arrangement of atoms is

known as a …………… plane.

a) lattice

b) crystal

c) metal

d) molecular


57. Laue experiment is used to produce diffraction in

………………...

a) gamma

b) UV

c) beta

d) X-rays


58. Bragg’s law is ……………….

a) 2d tanθ = λ

b) d Sinθ = n λ

c) 2d Sin θ = n λ

d) 2d Cos θ = n λ


59. Bragg’s spectrometer is used to measure the

wavelength of ……………

a) gamma

b) UV

c) beta

d) X-rays


60. The minimum wavelength of the radiation

emitted in continuous X-ray spectra λ min = ………

a) 12400Ao / V

b) 1240 Ao / V

c) 124 Ao / V

d) 124000Ao / V


61. When an electron jumps from M shell to the

K shell, it gives ………in the case of

characteristic X-rays.

a) Lβ line

b) K β line

c) Kα line

d) Mβ line


62. The frequency of the spectral line in the

characteristic X-rays is directly proportional to

the square of the atomic number of the

element. This is called ………………….

a) Moseley’s law

b) Stokes’s law

c) Newton’s law

d) Planck’s law


63. …………. has led to the discovery of new

elements like technetium, hafnium etc.

a) Planck’s law

b) Stokes’s law

c) Newton’s law

d) Moseley’s law


64. In normal population, the number atoms in

the ground state is ………… than the excited

state.

a) smaller

b) lesser

c) greater

d) lower


65. In population inversion, the number atoms in

the ground state is …………. than the excited

state.

a) higher

b) lesser

c) greater

d) more


66. The life time of atoms in the excited state is

normally ……………..

a) 10-6 second

b) 10-3 second

c) 10-8 second

d) 10-10 second


67. The life time of atoms in the metastable state

is normally ……………

a) 10-6 second

b) 10-3 second

c) 10-8 second

d) 10-10 second


68. A ruby is a crystal of ……………. , in which of

Al+3 ions are replaced by Cr+3 ions.

a) P2O5

b) Al2O6

c) Al2O2

d) Al2O3


69. The wavelength of green colour is ……………

a) 7500 Ao

b) 5500 Ao

c) 6943 Ao

d) 6328Ao


70. The wavelength of red colour is ………………

a) 7500 Ao

b) 5500 Ao

c) 6943 Ao

d) 6328Ao


71. He-Ne laser system consists of a quartz

discharge containing helium and neon in the

ratio of ….. at a pressure of about 1 mm of Hg.

a) 4 : 1 b) 1 : 2

c) 1 : 4 d) 2 : 1


72. The wavelength of the emitted photon in the

He-Ne laser system ……………..

a) 7500 Ao

b) 5500 Ao

c) 6943 Ao

d) 6328Ao


73. The beam that is used in endoscopy is …………

a) laser

b) maser

c) ordinary light

d) microwaves


74. The beam that is used in holography is ………

a) laser

b) maser

c) ordinary light

d) microwaves


75. The ……… action is based on the principle of

population inversion followed by stimulated

emission.

a) laser

b) maser

c) ordinary light

d) microwaves


76. The ……………. ions are used as maser

materials.

a) diamagnetic

b) paramagnetic

c) ferromagnetic

d) aluminum


77. Practical maser materials are often …………….

ions doped as impurities in ionic crystals.

a) chromium

b) sodium

c) potassium

d) calcium


78. ……………. is used in molecular spectroscopy.

a) laser

b) maser

c) ordinary light

d) microwaves


79. In optical fiber, ……………. laser is used.

a) metal

b) non-conducting

c) semiconductor

d) optical


80. The ratio of the radii of the first three orbits

of an atom is ……………

a) 1 : 2 : 3

b) 1 : 3 : 5

c) 1 : 4 : 9

d) 1: 3 : 9


81. The cathode rays are a stream of …………….

a) protons

b) photons

c) electrons

d) mesons


82. According to Bohr’s postulates, …………….

quantity take discrete values.

a) energy

b) momentum

c) radius

d) angular momentum


83. For hydrogen atom, the minimum energy

required to remove an electron from the first

orbit to the outermost orbit is …………. eV.

a) 13.6

b) 10.2

c) 5.4

d) infinity


84. According to Rutherford atom model, atoms

will give only …………… spectrum.

a) continuous

b) line

c) band

d) line absorption


85. The elliptical orbits of electron in the atom

were proposed by …………….

a) Thomson

b) Somerfield

c) Roentgen

d) Huygens


86. X ray is the phenomenon of conversion of

kinetic energy into ……………

a) radiation

b) potential energy

c) magnetic

d) electrostatic energy


87. The chromium ions doped in the ruby rod

absorbs …………… light.

a) red

b) blue

c) green

d) yellow


88. Canal rays travel …………. than the cathode

rays.

a) slower

b) faster

c) higher speed

d) none of the above


89. The spectra of alkali metals such as K, Na etc

cannot be explained by ……………. atom model.

a) Thomson

b) Somerfield

c) Roentgen

d) Huygens


90. In laser, all the photons are in …………. with

each other.

a) phase

b) face

c) pace

d) base


91. The cathode rays are

(a) a stream of electrons

(b) a stream of positive ions

(c) a stream of uncharged particles

(d) the same as canal rays


92. A narrow electron beam passes undeviated through an electric field E = 3 × 104 V/m and an overlapping magnetic field B = 2×10−3 Wb/m2. The electron motion, electric field and magnetic field are mutually perpendicular. The speed of the electron is

(a) 60 ms−1

(b) 10.3 × 107 ms−1

(c) 1.5 × 107 ms−1

(d) 0.67 × 10−7 ms−1


93. According to Bohr’s postulates, which of the

following quantities take discrete values?

(a) kinetic energy

(b) potential energy

(c) angular momentum

(d) momentum


94. The ratio of the radii of the first three Bohr

orbit is,

(a) 1 : 1/2 : 1/3

(b) 1 : 2 : 3

(c) 1 : 4 : 9

(d) 1 : 8 : 27


95. The first excitation potential energy or the

minimum energy required to excite the atom

from ground state of hydrogen atom is,

(a) 13.6 eV

(b) 10.2eV

(c) 3.4 eV

(d) 1.89 eV


96. According to Rutherford atom model, the

spectral lines emitted by an atom is,

(a) line spectrum

(b) continuous spectrum

(c) continuous absorption spectrum

(d) band spectrum


97. Energy levels A, B, C of a certain atom correspond to increasing values of energy (i.e.,) EA < EB < EC. If λ1, λ2, λ3 are the wavelengths of radiations corresponding to the transitions C to B, B to A and C to A respectively, which of the following statements is correct.

(a) λ3 = λ1 + λ2 (b)

(c) λ1 = λ2 + λ3 = 0 (d) λ23 = λ2

1 + λ22


21

213

98. The elliptical orbits of electron in the atom

were proposed by

(a) J.J.Thomson

(b) Bohr

(c) Sommerfeld

(d) de Broglie


99. X−ray is

(a) phenomenon of conversion of kinetic energy

into radiation.

(b) conversion of momentum

(c) conversion of energy into mass

(d) principle of conservation of charge


100. In an X-ray tube, the intensity of the emitted

X−ray beam is increased by

(a) increasing the filament current

(b) decreasing the filament current

(c) increasing the target potential

(d) decreasing the target potential


101. The energy of a photon of characteristic X-

ray from a Coolidge tube comes from

(a) the kinetic energy of the free electrons of

the target

(b) the kinetic energy of ions of the target

(c) the kinetic energy of the striking electron

(d) an atomic transition in the target.


102. A Coolidge tube operates at 24800 V. The

maximum frequency of X-radiation emitted

from Coolidge tube is

(a) 6 × 1018 Hz

(b) 3 × 1018 Hz

(c) 6 × 108 Hz

(d) 3 × 108 Hz


103. In hydrogen atom, which of the following

transitions produce a spectral line of maximum

wavelength

(a) 2 → 1

(b) 4 → 1

(c) 6 → 5

(d) 5 → 2


104. In hydrogen atom, which of the following

transitions produce a spectral line of maximum

frequency

(a) 2 → 1

(b) 6 → 2

(c) 4 → 3

(d) 5 → 2


105. After pumping process in laser,

(a) the number of atoms in the ground state is greater

than the number of atoms in the excited state.

(b) the number of atoms in the excited state is greater

than the number of atoms in the ground state.

(c) the number of atoms in the ground state is equal to

the number atoms in the excited state.

(d) No atoms are available in the excited state.


107. The chromium ions doped in the ruby rod

(a) absorbs red light

(b) absorbs green light

(c) absorbs blue light

(d) emits green light


Documents

12 TH STANDARD PHYSICS Prepared by: R.RAJENDRAN, M.A., M.Sc., M.Ed., N.INGARAN, M.Sc., M.Phil.,M.Ed., ATOMIC PHYSICS