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Wednesday, 15 June 2016

FSc ICS MCAT ECAT Physics Second Year Chapter 20 Atomic Spectra Choice Multiple Question (MCQ) Notes

FSc ICS MCAT ECAT Physics Second Year Chapter 20 Atomic Spectra Multiple Choice Question (MCQ) Notes

Both Bold and Underlined option is correct

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 Å
  • 400 Å
  • 720 Å
  • 912 Å

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(2π/h)
  • 2π/nh
  • nh/2π
  • n/2πh

56. The velocity of moving electron in nth orbit is given by the relation:
  • vn = nh/2πr
  • vn = n/πmr
  • vn = nhπm/r
  • vn = n(2)πmr/h

57. If the radius of first orbit of hydrogen atom is 0.53Å, the radius of second orbit will be:
  • 2.120 Å
  • 0.2120 Å
  • 21.200 Å
  • 0.142 Å

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 Å
  • 3055 Å
  • 8235 Å
  • 5230 Å

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

Written by: Asad Hussain

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