12 TH STANDARD PHYSICS 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 CHOOSE THE CORRECT ANSWER

3. Electrons were discovered by ……………… a) Millikan b) Goldstein c) Einstein d) Thomson CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

5. In a discharge tube, the potential difference applied between the two electrodes is ……………… a) V b) V c) V d) V CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

10. Canal rays were discovered by ……………….in the year a) Millikan b) Goldstein c) Einstein d) Thomson CHOOSE THE CORRECT ANSWER

11. In 1887, ………………… measured the specific charge of the cathode ray particles. a) Millikan b) Goldstein c) Einstein d) Thomson CHOOSE THE CORRECT ANSWER

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) V 2 / d CHOOSE THE CORRECT ANSWER

13. e / m value of the electron is ………………….. a) X C kg -1 b) X C kg c) X C kg -1 d) X C kg -1 CHOOSE THE CORRECT ANSWER

14. Millikan’s experiment is used for the measurement of ………… of the electron. a) density b) specific charge c) mass d) charge CHOOSE THE CORRECT ANSWER

15. In Millikan’s experiment, the potential difference applied between the two electrodes is ……… a) V b) V c) V d) V CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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) X C kg -1 b) X C kg c) X C kg -1 d) X C kg -1 CHOOSE THE CORRECT ANSWER

19. The concept of atoms was proposed by …………… a) Bohr b) Thomson c) Dalton d) Prout CHOOSE THE CORRECT ANSWER

20. Prout suggested that all elements are made up of atoms of ………………… a) carbon b) helium c) hydrogen d) nitrogen CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

22. In the case of hydrogen atom, Thomson’s model gives only one spectral line of about …………… a) 3300 A o b) 2300 A o c) 1300 A o d) 4300 A o CHOOSE THE CORRECT ANSWER

23. The scattering of α particles provide useful information about the structure of the ……………….. a) atom b) hydrogen c) CO 2 d) oxygen CHOOSE THE CORRECT ANSWER

24. The diameter of the atom is about ………….. a) m b) m c) m d) m CHOOSE THE CORRECT ANSWER

25. The diameter of the nucleus is about ……………. a) m b) m c) m d) m CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

27. An electron revolving in the stationary orbit does not radiate ………... a) lepton b) energy c) meson d) particle CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

30. Bohr radius value r1 = ………………… a) 0.63 A o b) 0.83 A o c) 0.53 A o d) 0.43 A o CHOOSE THE CORRECT ANSWER

31. The energy of the electron En = …………….. a) - z 2 me 4 / 8ε 0 2 n 2 h 2 b) z 2 me 4 / 8ε 0 2 n 2 h 2 c) n 2 h 2 ε 0 / π mze 2 d) - z 2 me 4 / 4ε 0 2 n 2 h 2 CHOOSE THE CORRECT ANSWER

32. 1 electron volt = ……………… J a) X b) X c) 9.11 X d) 9.11 X CHOOSE THE CORRECT ANSWER

33. Rydberg’s constant value R = ………………. a) X 10 7 m -1 b) X 10 9 c) X d) 9.11 X CHOOSE THE CORRECT ANSWER

34. The spectral lines of Lyman series of hydrogen atom lie in the ………… region. a) UV b) Visible c) infra - red d) gamma CHOOSE THE CORRECT ANSWER

35. The spectral lines of Balmer series of hydrogen atom lie in the …………….. a) UV b) Visible c) infra - red d) gamma CHOOSE THE CORRECT ANSWER

36. The spectral lines of Paschen series of hydrogen atom lie in the ………………. a) UV b) Visible c) infra - red d) gamma CHOOSE THE CORRECT ANSWER

37. The spectral lines of Brakett series of hydrogen atom lie in the ……………… a) UV b) Visible c) infra - red d) gamma CHOOSE THE CORRECT ANSWER

38. The spectral lines of Pfund series of hydrogen atom lie in the ………….. a) UV b) Visible c) infra - red d) gamma CHOOSE THE CORRECT ANSWER

39. The wavelengths of D1 and D2 lines of sodium are a) 5809A o,5896 A o b) 5986A o,5980 A o c) 5689A o,5690 A o d) 5896A o,5890 A o CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

42. The fine structure of spectral lines can not be explained by ………… theory. a) Raman b) Newton c) Bohr d) Huygens CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

45. X-rays were discovered by …………… a) Raman b) Newton c) Roentgen d) Huygens CHOOSE THE CORRECT ANSWER

46. X-rays are electromagnetic waves of short wavelength in the range of …………… a) 0.5 A o to 10 A o b) 0.5 A o to 100 A o c) 0.5 A o to 1000 A o d) 10 A o to 100 A o CHOOSE THE CORRECT ANSWER

47. Roentgen was awarded Nobel prize in 1901 for the discovery of ……………. a) gamma b) UV c) beta d) X-rays CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

49. In Coolidge tube, a high potential of about …………… is applied between filament F and the target T. a) V b) V c) V d) V CHOOSE THE CORRECT ANSWER

50. X-rays are of ……………. types. a) 3 b) 4 c) 2 d) 5 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

53. The penetrating power of hard X-rays is ……………. a) low b) very low c) high d) zero CHOOSE THE CORRECT ANSWER

54. When X-rays fall on certain metals, they liberate ………………… a) protons b) photons c) electrons d) mesons CHOOSE THE CORRECT ANSWER

55. To detect and measure the intensity of the X- rays, ………………. chamber is used. a) Thomson b) Bohr c) ionization d) Dalton CHOOSE THE CORRECT ANSWER

56. Any plane containing an arrangement of atoms is known as a …………… plane. a) lattice b) crystal c) metal d) molecular CHOOSE THE CORRECT ANSWER

57. Laue experiment is used to produce diffraction in ………………... a) gamma b) UV c) beta d) X-rays CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

59. Bragg’s spectrometer is used to measure the wavelength of …………… a) gamma b) UV c) beta d) X-rays CHOOSE THE CORRECT ANSWER

60. The minimum wavelength of the radiation emitted in continuous X-ray spectra λ min = ……… a) 12400A o / V b) 1240 A o / V c) 124 A o / V d) A o / V CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

64. In normal population, the number atoms in the ground state is ………… than the excited state. a) smaller b) lesser c) greater d) lower CHOOSE THE CORRECT ANSWER

65. In population inversion, the number atoms in the ground state is …………. than the excited state. a) higher b) lesser c) greater d) more CHOOSE THE CORRECT ANSWER

66. The life time of atoms in the excited state is normally …………….. a) second b) second c) second d) second CHOOSE THE CORRECT ANSWER

67. The life time of atoms in the metastable state is normally …………… a) second b) second c) second d) second CHOOSE THE CORRECT ANSWER

68. A ruby is a crystal of ……………., in which of Al +3 ions are replaced by Cr +3 ions. a) P 2 O 5 b) Al 2 O 6 c) Al 2 O 2 d) Al 2 O 3 CHOOSE THE CORRECT ANSWER

69. The wavelength of green colour is …………… a) 7500 A o b) 5500 A o c) 6943 A o d) 6328A o CHOOSE THE CORRECT ANSWER

70. The wavelength of red colour is ……………… a) 7500 A o b) 5500 A o c) 6943 A o d) 6328A o CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

72. The wavelength of the emitted photon in the He-Ne laser system …………….. a) 7500 A o b) 5500 A o c) 6943 A o d) 6328A o CHOOSE THE CORRECT ANSWER

73. The beam that is used in endoscopy is ………… a) laser b) maser c) ordinary light d) microwaves CHOOSE THE CORRECT ANSWER

74. The beam that is used in holography is ……… a) laser b) maser c) ordinary light d) microwaves CHOOSE THE CORRECT ANSWER

75. The ……… action is based on the principle of population inversion followed by stimulated emission. a) laser b) maser c) ordinary light d) microwaves CHOOSE THE CORRECT ANSWER

76. The ……………. ions are used as maser materials. a) diamagnetic b) paramagnetic c) ferromagnetic d) aluminum CHOOSE THE CORRECT ANSWER

77. Practical maser materials are often ……………. ions doped as impurities in ionic crystals. a) chromium b) sodium c) potassium d) calcium CHOOSE THE CORRECT ANSWER

78. ……………. is used in molecular spectroscopy. a) laser b) maser c) ordinary light d) microwaves CHOOSE THE CORRECT ANSWER

79. In optical fiber, ……………. laser is used. a) metal b) non-conducting c) semiconductor d) optical CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

81. The cathode rays are a stream of ……………. a) protons b) photons c) electrons d) mesons CHOOSE THE CORRECT ANSWER

82. According to Bohr’s postulates, ……………. quantity take discrete values. a) energy b) momentum c) radius d) angular momentum CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

84. According to Rutherford atom model, atoms will give only …………… spectrum. a) continuous b) line c) band d) line absorption CHOOSE THE CORRECT ANSWER

85. The elliptical orbits of electron in the atom were proposed by ……………. a) Thomson b) Somerfield c) Roentgen d) Huygens CHOOSE THE CORRECT ANSWER

86. X ray is the phenomenon of conversion of kinetic energy into …………… a) radiation b) potential energy c) magnetic d) electrostatic energy CHOOSE THE CORRECT ANSWER

87. The chromium ions doped in the ruby rod absorbs …………… light. a) red b) blue c) green d) yellow CHOOSE THE CORRECT ANSWER

88. Canal rays travel …………. than the cathode rays. a) slower b) faster c) higher speed d) none of the above CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

90. In laser, all the photons are in …………. with each other. a) phase b) face c) pace d) base CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

97. Energy levels A, B, C of a certain atom correspond to increasing values of energy (i.e.,) E A < E B < E C. If λ 1, λ 2, λ 3 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) λ 3 = λ 1 + λ 2 (b) (c) λ 1 = λ 2 + λ 3 = 0(d) λ 2 3 = λ λ 2 2 CHOOSE THE CORRECT ANSWER

98. The elliptical orbits of electron in the atom were proposed by (a) J.J.Thomson (b) Bohr (c) Sommerfeld (d) de Broglie CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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. CHOOSE THE CORRECT ANSWER

102. A Coolidge tube operates at V. The maximum frequency of X-radiation emitted from Coolidge tube is (a) 6 × Hz (b) 3 × Hz (c) 6 × 10 8 Hz (d) 3 × 10 8 Hz CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER

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. CHOOSE THE CORRECT ANSWER

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 CHOOSE THE CORRECT ANSWER