12th class (Fsc) Physics unit 9 MCQs
26. The unit of RH (Rydberg’s constant) is:
a. m2
b. ms-1
c. m-1
d. m
27. X-ray diffraction reveals that these are:
a. Particle type
b. Wave type
c. Both A & B
d. None of the above
28. In meta stable state electron stays for:
a. 10-8 s or more
b. 10-3 s or more
c. 10-8 s or less
d. 10-3 s or less
29. The radius of 10th orbit in hydrogen atom is:
a. 5.3 nm
b. 0.053 nm
c. 53 nm
d. 0.53 nm
30. Laser can be made by creating:
a. Excited state
b. Meta stable
c. Population inversion
d. All of these
31. Atom can reside in meta stable state for:
a. 10-3s
b. 10-1s
c. 10-4s
d. 10-2s
32. The equation of Rydbery constant is given by:
a. RH = Eo / λ
b. RH = hc/mo
c. RH = 1/hC
d. RH = Eo / hc
33. He-Ne laser discharge tube contain Neon:
a. 30%
b. 85%
c. 15%
d. 80%
34. Life time of meta stable is:
a. 10-8s
b. 10-5s
c. 10-2s
d. 10-3s
35. The value of radius of 1st Bohr’s orbit is:
a. 0.0053 nm
b. 0.053 nm
c. 0.00053 nm
d. 0.53 nm
36. The energy of the 4th orbit in hydrogen atom is:
a. -13.60 eV
b. -2.1 eV
c. -0.85 eV
d. -3.50 eV
37. Helium Neon laser beam emitted from discharge tube has a colour:
a. Red
b. Blue
c. Black
d. Green
38. The speed of an electron in nth orbit is given as:
a. 4πke/n2h2
b. 4π2 ke/ nh
c. 2π2 ke2 nh
d. 2πke2ke /nh
39. Laser is a beam of light which is:
a. Unidirectional
b. Monochromatic
c. Coherent
d. All of these
40. Radius of first orbit of an atom is r1 =0.053 nm:
a. 0.053 nm
b. 0.106 nm
c. 0.53×10-10nm
d. 0.212 nm
41. If electron jumps from second orbit to first orbit in hydrogen atom it emits photon of:
a. 13.6 eV
b. 3.40 eV
c. 3.8 eV
d. 10.20 eV
42. In Helium-Neon laser, discharge tube is filled with Neon gas:
a. 85%
b. 10%
c. 90%
d. 15%
43. In Helium Neon laser, the discharge tube is filled with:
a. 83% He, 17% Neon
b. 80% He, 20% Neon
c. 90% He, 10% Neon
d. 85% He, 15% Neon
44. The velocity of electron in 1st orbit of H-atom is:
a. 2.18×106m/sec
b. 2.09×106m/sec
c. 3.18×106m/sec
d. 2.19×106m/sec
45. In the meta stable the atoms can reside for:
a. 10-8s
b. 103s
c. 108s
d. 10-3s
46. Speed of the electron in the first Bohr’s orbit is:
a. 2.19×10-6cm/s
b. 2.19×106 m/sec
c. 2.19×10-6 cm/sec
d. 2.19×106 cm/sec
47. The first laser (Ruby Laser) was built by:
a. Peter Sorokin
b. Arthurs Schawlow
c. C.H Townes
d. T.H Maiman
48. The radius of first shell of hydrogen atom was quantized which is:
a. 0.53 nm
b. 0.0053 nm
c. 0.053 nm
d. 0.00053 nm
49. Which is not characteristics of LASER:
a. Intense
b. Monochromatic
c. Multi direction
d. Coherent
50. For Holography we use:
a. γ -rays
b. β– rays
c. X- rays
d. Laser
51. The unit of Rydberg’s constant is:
a. m-1
b. m
c. k-1
d. k
52. ……… has the largest do-Broglie wavelength at same speed.
a. Carbon atom
b. Proton
c. Electron
d. a-particle
53. The longest wavelength of Paschen series is:
a. 1875 nm
b. 656 nm
c. 2000 nm
d. 1094 nm
54. The mass spectrum of naturally occurring neon shows the most abundant isotope has atomic mass:
a. 21
b. 19
c. 22
d. 20
55. Paschen series lie in the:
a. infrared region
b. far-ultraviolet region
c. ultraviolet region
d. visible region
56. Radiation produced from TV picture tube is:
a. Infrared light
b. Gamma rays
c. Ultraviolet light
d. X-rays
57. X-rays are similar in nature to:
a. α-rays
b. β-rays
c. γ-rays
d. cathode rays
58. Metastable state of Neon is:
a. 18.70 eV
b. 20.66 eV
c. 1.60 eV
d. 20.61 eV
59. Bremsstrahlung radiations are example of:
a. Continuous spectra
b. Atomic spectra
c. Discrete spectra
d. Molecular spectra
60. The first orbit in the Hydrogen Atom has a radius:
a. 3.5×10-11m
b. 5.3×10-11m
c. 3.5×1011m
d. 5.3×1011m
61. The maximum K.E. of photoelectron depends upon:
a. Metal
b. Intensity of incident light
c. Temp. of Metal
d. Frequency of incident light
62. We can find from de Broglie formula:
a. Speed of wave
b. Wavelength
c. Frequency of wave
d. Amplitude
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