FSc ICS MCAT ECAT Physics Second Year Chapter 20 Atomic Spectra Multiple Choice Question (MCQ) Notes 2nd Year Physics Notes Online Taleem Ilmi Hub
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1. Quality of X-rays depends upon:
- Accelerating voltage
- Filament current
- Material of the target
- Both first and third
2. X-rays exhibit the phenomenon of:
- Diffraction
- Interference
- Polarization
- All of the above
3. The reverse process of photo-electric effect is called:
- Annihilation of matter
- Compton effect
- Pair production
- X-rays
4. The transition of inner shell electrons in heavy atoms give rise to the emission of:
- High energy photon or x-rays
- High energy γ rays
- Low energy photons or x-rays
- High energy β rays
5. The duration of a laser pulse is 10(-8) sec. The uncertainty in its energy will be:
- ΔE = h/Δt
- ΔE = hΔt
- ΔE = Δt/h
- None of the these
6. Characteristic of x-rays are produced from:
- Heavy element
- Light element
- Inner shell
- Both first and third
7. In the production of laser beam for each incident photon, we will have two photons going:
- In the same direction
- In opposite direction
- At right angle to each other
- In arbitrary direction
8. Reflecting mirrors in laser is used to:
- Further stimulation
- For producing more energetic lasers
- Both first and second
- None of these
9. In He-Ne laser, the laser action is produced by:
- Ne only
- He-Ne both
- Electrons of He
- Electrons Ne
10. The excited atoms returns to their ground state in:
- 10(-6) sec
- 10(-8) sec
- 10(-5) sec
- 10(-11) sec
11. Life time of meta-stable states is:
- 10(-6) sec or more
- 10(-3) sec or more
- 10(-5) sec or more
- None of these
12. If the speed of light were 2/3 of its present value, the energy released in a given atomic explosion will be decreased by a fraction of:
- 2/3
- 4/9
- 5/9
- 2/9
13. Helium-Neon laser discharge tube contains neon:
- 82 %
- 15 %
- 25 %
- 85 %
14. Laser can be made by creating:
- Population inversion
- Metastable state
- Assembly
- All of the above
15. What is the speed of electron in the first Bohr orbit?
- 2.19 * 10(6) m/s
- 1.6 * 10(6) m/s
- 2.2 * 10(-6) m/s
- 3 * 10(8) m/s
16. The dual nature of light is exhibited by:
- Diffraction and photoelectric effect
- Diffraction and reflection
- Refraction and interference
- Photoelectric effect
17. The size of the atom is approximately equal to:
- 10(-4) cm or 10(-6) meter
- 10(-6) cm or 10(-8) meter
- 10(-8) cm or 10(-10) meter
- 10(-12) cm or 10(-14) meter
18. According to Bohr's postulates which of the following quantities takes discrete values?
- Kinetic energy
- Potential energy
- Angular momentum
- Momentum
19. According to Bohr principle, the relation between main quantum number (n) and radius of orbit (r) is:
- r ∝ 1/n
- r ∝ n
- r ∝ n(2)
- r ∝ 1/n(2)
20. The radius of electron's second stationary orbit in Bohr's atom is R. The radius of the third orbit will be:
- 3 R
- 2.25 R
- 9 R
- R/3
21. According to Bohr when electron jumps from any higher orbit to third orbit, the spectral lines so emitted are called:
- Balmer series
- Paschen series
- Lyman series
- P.fund series
22. The ratio of the energies of the hydrogen atom in its first to second excited states is:
- 1/4
- 4/9
- 9/4
- 4
23. Of the various series of the hydrogen spectrum, the one which lies wholly in the ultraviolet region is:
- Lyman series
- Balmer series
- Paschen series
- Brackett series
24. The speed of an electron in the orbit of hydrogen atom in the ground state is:
- c
- c/10
- c/2
- c/137
25. Hydrogen atoms are excited from ground state to the state of principal quantum number 4. Then the number of spectral lines observed will be:
- 3
- 6
- 5
- 2
26. The angular momentum of an electron in a hydrogen atom is proportional to:
- 1/√r
- 1/r
- √r
- r(2)
27. The required energy to detach one electron from Balmer series of hydrogen spectrum is:
- 13.6 eV
- 10.2 eV
- 3.4 eV
- -1.5 eV
28. The total energy of the electron in the hydrogen atom in the ground state is -13.6 eV. The K.E of this electron is:
- 13.6 eV
- 0 eV
- -13.6 eV
- 6.8 eV
29. Which of the following electromagnetic waves have the smallest wavelength?
- γ-rays
- X-rays
- UV-rays
- Infrared rays
30. An electromagnetic radiation has an energy of 13.2 KeV. Then the radiation belongs to the region of:
- Visible light
- Ultraviolet
- Infrared
- Microwave
31. The shortest wavelength of X-rays emitted from an X-ray tube depends on the:
- Current in the tube
- Voltage applied to the tube
- Nature of the gas in the tube
- Atomic number of the target
32. The wavelength of X-rays is nearer to the order of:
- 10(-2) m
- 10(-4) m
- 10(-8) m
- 10(-10) m
33. The characteristic of the target element that determines the frequency of characteristic X-rays, is:
- its mass number
- its atomic number
- its melting point
- its conductivity
34. On increasing the number of electrons striking the anode of an X-ray tube, which one of the following parameters of the resulting X-ray would increase.
- Penetration power
- Frequency
- Wavelength
- Intensity
35. The voltage applied across an X-ray tube is nearly:
- 10 volt
- 100 volt
- 10000 volt
- 10(6) volt
36. X-rays were discovered by:
- Roentgen
- Becquerel
- Marie Curie
- Van Lave
37. Which of the following lies wholly in the ultraviolet region?
- Lyman series
- Paschen series
- Brackett series
- Balmer series
38. The Balmer series of hydrogen results when electron jumps from higher orbits to:
- 1st orbit
- 2nd orbit
- 3rd orbit
- 4th orbit
39. What is the ratio of the velocity of electron in third Bohr's orbit to the velocity in 2nd orbit?
- 9/4
- 2/3
- 3/2
- 4/9
40. Dimension of Rydberg constant is:
- LT(-1)
- L(-1)T
- L(-1)
- None of these
41. To find longest wavelength radiation in Balmer series the value of 'n' used is:
- 2
- 3
- 4
- ∞
42. The ionization energy of hydrogen is:
- 13.6 eV
- -13.6 eV
- 3.4 eV
- Zero
43. By CAT scans we can detect the density difference of the order of:
- 1 %
- 15 %
- 10 %
- 50 %
44. The longest wavelength of light which ionizes a hydrogen atom is:
- 0.74 Ã…
- 400 Ã…
- 720 Ã…
- 912 Ã…
45. The ratio of minimum to maximum wavelength in Balmer series is:
- 5 : 9
- 5 : 36
- 1 : 4
- 3 : 4
46. X-rays and γ-rays of same energies may be distinguished by:
- Method of production
- Their intensities
- Ionizing power
- Their velocities
47. Atomic hydrogen is excited to the 8th energy level. How many spectral lines can be observed in spectrum?
- 8
- 16
- 28
- 64
48. Compton effect is associated with:
- γ-rays
- Positive rays
- β-rays
- X-rays
49. Which of the following types of electromagnetic waves have the longest wavelength?
- X-rays
- Infrared
- Radio waves
- Visible light
50. Which of the following radiation series is found in the visible region?
- Lyman
- Paschen
- Pfund
- Balmer
51. The ground state energy of H-atom is 13.6 eV. The energy needed to ionize H-atom from its second excited state is:
- 1.51 eV
- 3.4 eV
- 13.6 eV
- 12.1 eV
52. Line spectrum is obtained whenever the incandescent vapours at low pressure of the excited substance are it their:
- Atomic state
- Molecular state
- Nuclear state
- None of these
53. In black and white televisions, pictures on the screen are produced due to bombardment of:
- X-ray photons on a white screen
- X-ray photons on a white fluorescent screen
- Electrons on a white screen
- Electrons on a fluorescent screen
54. The value of Rydberg constant is:
- 1.0974 * 10(-7) m(-1)
- 1.0974 * 10(7) m(-1)
- 1.0974 * 10(7) m(-2)
- 10.0974 * 10(7) m(-1)
55. According to Bohr's theory of the hydrogen atom. Only those orbits around the nucleus are allowed along with angular momentum of electron is:
- n(2Ï€/h)
- 2Ï€/nh
- nh/2Ï€
- n/2Ï€h
56. The velocity of moving electron in nth orbit is given by the relation:
- vn = nh/2Ï€r
- vn = n/Ï€mr
- vn = nhπm/r
- vn = n(2)Ï€mr/h
57. If the radius of first orbit of hydrogen atom is 0.53Ã…, the radius of second orbit will be:
- 2.120 Ã…
- 0.2120 Ã…
- 21.200 Ã…
- 0.142 Ã…
58. In an electronic transition, atom cannot emit:
- γ-rays
- Infrared radiation
- Visible light
- Ultra violet rays
59. The shortest wavelength radiation in Balmer series is:
- 3645 Ã…
- 3055 Ã…
- 8235 Ã…
- 5230 Ã…
60. The maximum frequency f(max) of X-rays produced by the electrons accelerated by a potential of Vo volts can be expressed by:
- f(max) = h/Ve
- f(max) = Ve/h
- f(max) = hV
- f(max) = V/hc
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