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66. An electron (m = 9.11 × 10 31 kg, q = 1.60 × 10 19 C) travels at 0.95c around a circular orbit
perpendicular to a uniform 1.8-T magnetic field. The radius of its orbit is:
A. 0.28 mm
B. 0.90 mm
C. 1.1 mm
D. 2.9 mm
E. 4.7 mm
ans: D
67. An electron (m = 9.11 × 10 31 kg, q = 1.60 × 10 19 C) travels around a 1.7-mm radius circular
orbit perpendicular to a 2.8-T magnetic field. Its speed is:
A. 0.16c
B. 0.36c
C. 0.94c
D. c
E. 2.8c
ans: C
Chapter 37:
SPECIAL THEORY OF RELATIVITY
573
Chapter 38:
PHOTONS AND MATTER WAVES
1. The units of the Planck constant h are those of:
A. energy
B. power
C. momentum
D. angular momentum
E. frequency
ans: D
2. If h is the Planck constant, then ¯ is:
h
A. 2 h
B. 2h
C. h/2
D. h/2
E. 2h/
ans: D
3. The quantization of energy, E = nhf , is not important for an ordinary pendulum because:
A. the formula applies only to mass-spring oscillators
B. the allowed energy levels are too closely spaced
C. the allowed energy levels are too widely spaced
D. the formula applies only to atoms
E. the value of h for a pendulum is too large
ans: B
4. The frequency of light beam A is twice that of light beam B. The ratio EA /EB of photon
energies is:
A. 1/2
B. 1/4
C. 1
D. 2
E. 4
ans: D
5. The wavelength of light beam B is twice the wavelength of light beam B. The energy of a
photon in beam A is:
A. half the energy of a photon in beam B
B. one-fourth the energy of a photon in beam B
C. equal to the energy of a photon in beam B
D. twice the energy of a photon in beam B
E. four times the energy of a photon in beam B
ans: A
574
Chapter 38:
PHOTONS AND MATTER WAVES
6. A photon in light beam A has twice the energy of a photon in light beam B. The ratio pA /pB
of their momenta is:
A. 1/2
B. 1/4
C. 1
D. 2
E. 4
ans: D
7. Which of the following electromagnetic radiations has photons with the greatest energy?
A. blue light
B. yellow light
C. x rays
D. radio waves
E. microwaves
ans: C
8. Which of the following electromagnetic radiations has photons with the greatest momentum?
A. blue light
B. yellow light
C. x rays
D. radio waves
E. microwaves
ans: C
9. Rank following electromagnetic radiations according to the energies of their photons, from least
to greatest.
1. blue light
2. yellow light
3. x rays
4. radio waves
A. 1, 2, 3, 4
B. 4, 2, 1, 3
C. 4, 1, 2, 3
D. 3, 2, 1, 4
E. 3, 1, 2, 4
ans: B
10. The intensity of a uniform light beam with a wavelength of 500 nm is 2000 W/m2 . The photon
flux (in number/m 2 · s) is about:
A. 5 × 1017
B. 5 × 1019
C. 5 × 1021
D. 5 × 1023
E. 5 × 1025
ans: C
Chapter 38:
PHOTONS AND MATTER WAVES
575
11. The concentration of photons in a uniform light beam with a wavelength of 500 nm is 1.7 ×
1013 m 3 .
(…)
…/m for electrons provides evidence of the:
A. wave nature of matter
B. particle nature of matter
C. wave nature of radiation
D. particle nature of radiation
E. transverse wave nature of light
ans: B
31. Evidence for the wave nature of matter is:
A. electron di raction experiments of Davisson and Germer
B. Thompson’s measurement of e/m
C. Young’s double slit experiment
D. the Compton e ect
E. Lenz’s…
… what property of the electron in a
hydrogen atom?
A. Energy
B. Orbital angular momentum
C. Spin angular momentum
D. Magnetic moment
E. z component of angular momentum
ans: A
25. Take the potential energy of a hydrogen atom to be zero for infinite separation of the electron
and proton. Then, according to quantum theory the energy En of a state with principal
quantum number n is proportional to:
A. n
B…
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