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Chapter 27 (modern physics)
1. Planck’s quantum theory is compatible with the experimental data related to which of the following?
a. blackbody radiation b. the photoelectric effect c. line spectra emitted by hydrogen gas d. all of the above
2. Blue light will not eject electrons from a certain metal; however, which one of the following may possibly eject electrons from that metal?
a. infra‑red b. ultra‑violet c. red d. green
3. Light of wavelength 6.5 ´ 10‑7 m has an energy of: (h = 6.63 ´ 10-34 J‑s)
a. 3.1 ´ 10‑19 J b. 3.3 ´ 10‑19 J c. 1.5 ´ 10‑19 J d. 1.7 ´ 10‑19 J
4. If a monochromatic light beam with quantum energy value of 3.0 eV incident upon a photocell where the work function of the target metal is 1.60 eV, what is the maximum kinetic energy of ejected electrons?
a. 4.6 eV b. 4.8 eV c. 1.4 eV d. 2.4 eV
5. Which of the following devices represent(s) a practical application of the photoelectric effect?
a. hologram b. camera light intensity meter c. both of the above choices d. none of the above
6. According to the de Broglie hypothesis, which of the following statements is applicable to the wavelength of a moving particle?
a. directly proportional to its energy b. directly proportional to its momentum c. inversely proportional to its energy d. inversely proportional to its momentum 7. If the measured momentum of an electron is 3.20 ´ 10‑27 kg‑m/s with an uncertainty of 1.6 ´ 10‑29 kg‑m/s, what is the minimum uncertainty in the determination of its position? (h = 6.63 ´ 10‑34 J‑S)
a. 2.6 ´ 10‑8 m b. 3.3 ´ 10‑6 m c. 0.63 ´ 10-4 m d. 1.1 ´ 10‑3 m
8. As the temperature of a radiation emitting blackbody becomes higher, what happens to the peak wavelength of the radiation?
a. increases b. decreases c. remains constant d. is directly proportional to temperature
9. According to Einstein, what is true of the stopping potential for a photoelectric current as the wavelength of incident light becomes shorter?
a. increases b. decreases c. remains constant d. stopping potential is directly proportional to wavelength
10. According to Einstein, as the wavelength of the incident monochromatic light beam becomes shorter, the work function of a target material in a phototube:
a. increases b. decreases c. remains constant d. work function is directly proportional to wavelength
11. According to de Broglie, as the momentum of a moving particle is tripled, the corresponding wavelength changes by what factor?
a. 1/9 b. 1/3 c. 3.0 d. 9.0
12. According to Heisenberg, as the uncertainty in the measurement of a particle’s momentum is reduced by a factor of 2, by what factor is the uncertainty in that same particle’s position changed?
a. 1/2 b. 3.0 c. 2.0 d. 9.0
13. What is the frequency of monochromatic light where the photon energy is 5.5 ´ 10‑19 J? (h = 6.63 ´ 10‑34 J‑s)
a.2.2 ´ 1014 Hz b. 4.4 ´ 1014 Hz c. 8.3 ´ 1014 Hz d. 9.8 ´ 1014 Hz
14. What is the wavelength of a monochromatic light beam, where the photon energy is 5.0 ´ 10‑19 J? (h = 6.63 ´ 10‑34 J‑s, c = 3 ´ 108 m/s and 1 nm = 10‑9 m)
a. 354 nm b. 398 nm c. 414 nm d. 787 nm
15. What is the wavelength of a monochromatic light beam where the photon energy is 2.0 eV? (h = 6.63 ´ 10‑34 J‑s, c = 3 ´ 108 m/s, 1 nm = 10‑9 m and 1 eV = 1.6 ´ 10‑19 J)
a. 414 nm b. 621 nm c. 746 nm d. 829 nm
16. A monochromatic light beam is incident on a barium target, which has a work function of 2.50 eV. If a stopping potential of 1.0 V is required, what is the light beam photon energy?
a. 1.0 eV b. 1.5 eV c. 2.5 eV d. 3.5 eV
17. A light beam is shining on a metal target which has a work function of 2.20 eV. If a stopping potential of 1.3 V is required, what is the wavelength of the incoming monochromatic light? (h = 6.63 ´ 10‑34 J‑s, c = 3 ´ 108 m/s, 1 eV = 1.6 ´ 10‑19 J and 1 nm = 10‑9 m)
a. 355 nm b. 497 nm c. 744 nm d. 1421 nm 18. Light of wavelength 450 nm is incident on a target metal which has a work function of 1.8 eV. What stopping potential is required for this combination in a phototube? (h = 6.63 ´ 10‑34 J‑s, c = 3 ´ 108 m/s, 1 eV = 1.6 ´ 10‑19 J and 1 nm = 10‑9 m)
a. 0.57 V b. 0.96 V c. 2.76 V d. 4.56 V
19. If barium has a work function of 2.60 eV, what is its cutoff wavelength when used as a phototube target? (h = 6.63 ´ 10‑34 J‑s, c = 3 ´ 108 m/s, 1 eV = 1.6 ´ 10‑19 J and 1 nm = 10‑9 m)
a. 398 nm b. 477 nm c. 497 nm d. 596 nm
20. What in the de Broglie wavelength for a proton (m = 1.67 ´ 10‑27 kg) moving at a speed of 5.0 ´ 105 m/s? (h = 6.63 ´ 10‑34 J‑s)
a. 1.1 ´ 10‑12 m b. 0.42 ´ 10‑12 m c. 1.8 ´ 10‑12 m d. 0.79 ´ 10‑12 m
21. The de Broglie wavelength of a 0.06 kg golf ball is 4.28 ´ 10‑34 m. Find its speed.
a. 15 m/s b. 26 m/s c. 31 m/s d. 48 m/s
22. The electron microscope’s main advantage over the optical microscope is which of the following?
a. greater ease of portability b. dispenses with need for a lens c. higher power lens used d. higher resolution possible
23. The wave function as derived in Schrodinger’s equation is best described as being a measure of which of the following?
a. photon beam frequency b. photon wavelength c. particle wavelength d. probability
24. What is the minimum X‑ray wavelength produced when electrons are accelerated through a potential of 50,000 V? (h = 6.63 ´ 10‑34 J‑s, c = 3 ´ 108 m/s and 1 eV = 1.6 ´ 10‑19 J)
a. 12.4 ´ 10‑12 m b. 16.5 ´ 10‑12 m c. 19.8 ´ 10‑12 m d. 24.9 ´ 10‑12 m
25. The Compton experiment demonstrated which of the following when an X‑ray photon collides with an electron?
a. momentum is conserved b. energy is conserved c. momentum and energy are both conserved d. wavelength of scattered photon equals that of incident photon
26. What is the energy of a photon whose frequency is 6 ´ 1020 Hz? (h = 6.63 ´ 10‑34 J‑s and 1 eV = 1.6 ´ 10‑19 J)
a. 1.6 MeV b. 2.5 MeV c. 3.3 MeV d. 4.8 MeV
27. A quantum of radiation has an energy of 2 keV. What is its frequency? (h = 6.63 ´ 10‑34 J‑s and 1 eV = 1.6 ´ 10‑19 J)
a. 3.2 ´ 1017 Hz b. 4.8 ´ 1017 Hz c. 6.3 ´ 1017 Hz d. 7.3 ´ 1017 Hz
28. If a quantum of radiation has an energy of 2 keV, what is its wavelength? (h = 6.63 ´ 10‑34 J‑s, 1 eV = 1.6 ´ 10‑19 J. c = 3 ´ 108 m/s and 1 nm = 10‑9 m)
a. 0.32 nm b. 0.41 nm c. 0.62 nm d. 1.02 nm
29. An ultraviolet light beam having a wavelength of 130 nm is incident on a molybdenum surface with work function of 4.2 eV. What is the stopping potential? (h = 6.63 ´ 10‑34 J‑s, c = 3 ´ 108 m/s, 1 eV = 1.6 ´ 10‑19 J and 1 nm = 10‑9 m)
a. 1.3 V b. 3.5 V c. 5.4 V d. 11.9 V
30. Blue light (l = 460 nm) is incident on a piece of potassium (f = 2.2 eV). What is the maximum kinetic energy of the ejected photoelectrons? (h = 6.626 ´ 10‑34 J‑s, c = 3 ´ 108 m/s, 1 eV = 1.6 ´ 10‑19 J)
a. 1.0 eV b. 0.5 eV c. 0.25 eV d. 4.9 eV
31. Light of wavelength 480 nm is incident on a metallic surface with a resultant photoelectric stopping potential of 0.55 V. What is the work function of the metal? (h = 6.63 ´ 10‑34 J‑s, c = 3 ´ 108 m/s, 1 eV = 1.6 ´ 10‑19 J and 1 nm = 10‑9 m)
a. 2.04 eV b. 3.19 eV c. 2.59 eV d. 0.55 eV
32. If the minimum X‑ray wavelength produced is 13.5 ´ 10‑12 m, through what potential are the electrons accelerated in order to generate this radiation? (h = 6.63 ´ 10‑34 J‑s, c = 3 ´ 108 m/s and 1 eV = 1.6 ´ 10‑19 J)
a. 33,000 V b. 46,040 V c. 75,000 V d. 92,080 V
33. According to Wien’s displacement law, if the absolute temperature of a radiating blackbody is tripled, then the peak wavelength emitted will change by what factor?
a. 1/3 b. 1.0 c. 3.0 d. 9.0 34. What is the surface temperature of a distant star (which emits light as if it were a blackbody) where the peak wavelength is 480 nm?
a. 4510 K b. 5100 K c. 6038 K d. 6350 K
35. X‑rays of wavelength of 0.0650 nm undergo Compton scattering from free electrons in carbon. What is the wavelength of photons scattered at 90˚ relative to the incident beam? (h = 6.63 ´ 10‑34 J‑S, me = 9.11 ´ 10‑31 kg, c = 3 ´ 108 m/s and 1 nm = 10‑9 m)
a. 0.0024 nm b. 0.0674 nm c. 0.0687 nm d. 0.0626 nm
36. In regard to the Compton scattering experiment with X-rays incident upon a carbon block, as the scattering angle becomes larger, what happens to the magnitude of difference between the incident and scattered wavelengths?
a. increases b. decreases c. remains constant d. difference is maximum at 45˚ angle of scatter
37. Which of the following statements best describes the relation between the quantum theory and the photoelectric effect experiment?
a. quantum theory explains photoelectric effect b. photoelectric effect contradicts quantum theory c. quantum theory has no bearing on photoelectric effect d. photoelectric effect explains quantum theory
38. An electron accelerated through a potential difference of 40 V. What is its de Broglie wavelength? (h = 6.63 ´ 10‑34 J‑s, me = 9.11 ´ 10‑31 kg and 1 eV = 1.67 ´ 10‑19 J)
a. 1.14 ´ 10-10 m b. 1.48 ´ 10‑10m c. 1.90 ´ 10‑10 m d. 2.34 ´ 10‑10 m
39. If an electron has a measured wavelength of 0.85 ´ 10-10 m, what is its kinetic energy? (h = 6.63 ´ 10‑34 J‑s, 1 eV = 1.6 ´ 10‑19 J. and me = 9.11 ´ 10‑31 kg)
a. 55 eV b. 104 eV c. 147 eV d. 209 eV
40. A sodium vapor lamp has a power output of 300 W. If 590 nm is the average wavelength of the source, about how many photons are emitted per second? (h = 6.63 ´ 10‑34 J‑s, c = 3 ´ 108 m/s and 1 nm = 10‑9 m)
a. 1017 b. 1021 c. 1025 d. 1029
41. Consider a hollow body with a small hole in one side. If this is a black body, it must:
a. be filled with gas. b. emit no light. c. have black paint on the walls. d. contain electromagnetic radiation.
42. Classical theories predict that most of the energy from a black body should be radiated:
a. as thermal radiation in the infrared region. b. at the wavelength given by Wien's displacement law. c. as ultraviolet light. d. a black body should not radiate
43. The ultraviolet catastrophe predicts that:
a. all objects should radiate extreme amounts of ultraviolet light. b. as an object gets hotter its light will change from dull red to blue white. c. a black body can absorb an infinite amount of radiation if the radiation is in the ultraviolet region. d. the radiated energy approaches zero as the wavelength approaches zero.
44. According to Einstein, increasing the brightness of a beam of light without changing its color will increase:
a. the number of photons. b. the energy of each photon. c. the speed of the photons. d. the frequency of the photons.
45. A photon absorbed by an electron will give up more energy to the electron if the photon
a. is not spread out over many electrons. b. is moving faster. c. is moving slower. d. has a higher frequency.
46. Which change will not change the kinetic energy of the most energetic electrons emitted in the photoelectric effect?
a. changing the brightness of the light b. changing the frequency of the light c. changing the metal the light is hitting d. all of the above will change the electron’s kinetic energy 47. The spacing between atoms in KCl crystal is 3.1 ´ 10‑10m. At what angle from the surface will a beam of 3.14 ´ 10‑11m X‑rays be constructively scattered?
a. 57˚ b. 2.9˚ c. 90˚ d. 10˚
48. X‑ray production occurs in which process?
a. photons hitting a metal, emitting electrons b. electrons hitting a metal, emitting photons c. photons hitting a metal, emitting X‑rays d. electrons hitting a metal and scattering elastically
49. Changing the accelerating voltage of an X‑ray machine without changing the target material must change:
a. the work function of the material. b. the wavelength of all the X‑rays produced. c. the wavelength of the minimum wavelength X‑ray that will be produced. d. both b and c are correct
50. An important use of X‑ray diffraction was:
a. the observation of Compton scattering. b. determining the structure of the DNA molecule. c. production of positrons. d. observation of the photoelectric effect.
51. Which process cannot occur if only one photon is involved?
a. pair annihilation b. pair production c. the photoelectric effect d. X‑ray production
52. According to the principle of complementarily, everything acts in a given experiment as if it is either a wave or a particle. In which experiment is the wave aspect exhibited?
a. the Davisson and Germer experiment b. the photoelectric effect c. pair production d. Compton scattering
53. A helium‑neon laser emits red light having a wavelength of 632.8 nm and a power of 0.5 mW. How many photons are emitted each second? (h = 6.626 ´ 10‑34 J‑s)
a. 1.6 ´ 1015 b. 3.3 ´ 1016 c. 4.8 ´ 1017 d. 2.6 ´ 1018
54. How much energy (in eV) does a photon of red light (l = 640 nm) have? (h = 6.626 ´ 10‑34 J‑s and 1 eV = 1.6 ´ 10‑19 J)
a. 3.2 eV b. 2.5 eV c. 1.9 eV d. 1.3 eV
55. In an X‑ray diffraction experiment, using X‑rays of wavelength l = 0.5 ´ 10‑10 m, a first‑order maximum occurred at 5˚ off the crystal plane. Find the distance d between crystal planes.
a. 2.87 ´ 10‑10 m b. 1.36 ´ 10‑10 m c. 6.24 ´ 10‑9 m d. 1.93 ´ 10‑9 m
56. What is the maximum velocity of a photoelectron emitted from a surface with work function 5 eV when illuminated by 200 nm ultraviolet light? (melectron = 9.1 ´ 10‑31 kg, h = 6.626 ´ 10‑34 J‑s, 1 eV = 1.6 ´ 10‑19 J)
a. 800,080 m/s b. 652,800 m/s c. 431,100 m/s d. 212,200 m/s
57. An electron microscope operates with electrons of kinetic energy 40 keV. What is the wavelength of these electrons? (h = 6.626 ´ 10‑34 J‑s, 1 eV = 1.6 ´ 10‑19 J. and me = 9.1 ´ 10‑31 kg)
a. 0.50 ´ 10‑10 m b. 7.17 ´ 10‑11 m c. 6.14 ´ 10‑12 m d. 3.07 ´ 10‑13 m 58. An electron and a positron both of rest mass 0.57 MeV slowly drift together and annihilate into two gamma ray photons. What is the wavelength of each of the photons?
a. 1.21 ´ 10‑12 m b. 2.43 ´ 10‑12 m c. 4.86 ´ 10‑12 m d. 9.72 ´ 10‑12 m
59. A proton (mass = 1.67 ´ 10‑27 kg) has a kinetic energy of 1 MeV. If its momentum is measured with an uncertainty of 1%, what is the minimum uncertainty in its position? (h = 6.626 ´ 10‑34 J‑s)
a. 9.08 ´ 10‑13 m b. 2.28 ´ 10‑13 m c. 9.08 ´ 10‑14 m d. 5.64 ´ 10‑14 m
60. The “seeing” ability or resolution of radiation is determined by its wavelength. If the size of an atom is approximately 10‑10 m, how fast must an electron travel to have a wavelength smaller than that of an atom? (me = 9.1 ´ 10‑31 kg, h = 6.626 ´ 10‑34 J‑s)
a. 7.28 ´ 106 m/s b. 3.39 ´ 106 m/s c. 1.03 ´ 106 m/s d. 5.35 ´ 105 m/s
Chapter 27 - Answers
# Ans Difficulty # Ans Difficulty 1. D 1 31. A 2 2. B 1 32. D 2 3. A 2 33. A 1 4. C 1 34. C 2 5. B 1 35. B 3 6. D 1 36. A 2 7. B 2 37. A 1 8. B 1 38. C 2 9. A 1 39. D 2 10. C 1 40. B 2 11. B 1 41. D 1 12. C 1 42. C 1 13. C 1 43. A 1 14. B 2 44. A 1 15. B 2 45. D 1 16. D 1 46. A 2 17. A 2 47. B 2 18. B 3 48. B 1 19. B 3 49. C 1 20. D 2 50. B 1 21. B 2 51. A 2 22. D 1 52. A 2 23. D 1 53. A 2 24. D 2 54. C 2 25. C 2 55. A 2 26. B 2 56. B 2 27. B 2 57. C 2 28. C 2 58. B 3 29. C 2 59. B 2 30. B 2 60. A 3 |
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