Section 30.7 X-rays
58. In an X-ray tube, electrons with energy 35 keV are incident on a cobalt (Z = 27) target. Determine the cutoff wavelength for X-ray production.
(a) 1.4 1011 m (c) 2.8 1011 m (e) 3.6 1011 m
(b) 1.8 1011 m (d) 3.2 1011 m
59. Which electron energy will produce the lowest cutoff wavelength for X-ray production from a nickel (Z = 28) surface?
(a) 25 keV (c) 35 keV (e) 45 keV
(b) 30 keV (d) 40 keV
60. Which one of the following statements concerning the cutoff wavelength typically exhibited in X-ray spectra is true?
(a) The cutoff wavelength depends on the target material.
(b) The cutoff wavelength depends on the potential difference across the X-ray tube.
(c) The cutoff wavelength is independent of the energy of the incident electrons.
(d) The cutoff wavelength occurs because of the mutual shielding effects of K-shell electrons.
(e) The cutoff wavelength occurs because an incident electron cannot give up all of its energy.
61. Calculate the K X-ray wavelength for a gold atom (Z = 79).
(a) 5.13 1010 m (c) 2.00 1011 m (e) 2.47 1013 m
(b) 8.54 1010 m (d) 3.60 1011 m
62. Electrons in an X-ray tube are accelerated through a potential difference of 40 kV. The electrons then strike a zirconium (Z = 40) target. Determine the cutoff frequency for X-ray production.
(a) 4.7 1019 Hz (c) 3.2 1018 Hz (e) 1.1 1016 Hz
(b) 9.7 1018 Hz (d) 6.7 1017 Hz
63. What is the operating voltage of a medical X-ray machine that has a cut-off wavelength of 2.20 10–11 m?
(a) 83 800 V (c) 30 700 V (e) 56 500 V
(b) 10 900 V (d) 44 900 V
Section 30.8 The Laser
Section 30.9 Medical Applications of the Laser
Section 30.10 Holography
64. Complete the following sentence: In the condition known as population inversion,
(a) the amount of one type of gas atoms is larger than that of another in a mixture.
(b) the number of energy levels that are populated is larger than that of unpopulated levels.
(c) there are more electrons occupying lower energy levels than occupying higher energy levels.
(d) there are more electrons occupying higher energy levels than occupying lower energy levels.
(e) there are more photons than electrons in a given system.
65. An argon-ion laser emits a blue-green beam of light with a wavelength of 488 nm in a vacuum.
What is the difference in energy in joules between the two energy states for the atomic transition that produces this light?
(a) 4.08 1019 J (c) 6.18 1020 J (e) 5.10 1028 J
(b) 1.05 1020 J (d) 4.76 1024 J
66. A pulsed laser has an average output power of 4.0 W. Each pulse consists of light at wavelength 5.0 107 m and has a 25 ms duration. How many photons are emitted in a single pulse?
(a) 1.0 1017 (c) 3.7 1017 (e) 7.4 1017
(b) 2.5 1017 (d) 5.0 1017
67. An electron makes a transition from a higher energy state to a lower one without any external provocation. As a result of the transition, a photon is emitted and moves in a random direction.
What is the name of this emission process?
(a) stationary emission (c) spectral emission (e) specular emission
(b) stimulated emission (d) spontaneous emission
68. Complete the following statement: In the laser-based medical procedure known as photorefractive keratectomy (PRK), nearsightedness and farsightedness can be treated using the laser to
(a) remove small amounts of tissue from the lens and change its curvature.
(b) remove small amounts of tissue from the cornea and change its curvature.
(c) change the index of refraction of the aqueous humor.
(d) alter the fluid pressure within the eye.
(e) stimulate unused rods and cones on the retina.
69. Complete the following sentence: Holography is
(a) the projection of an image produced by a combination of mirrors and lenses.
(b) a photograph of the light produced by a laser.
(c) a process for producing three dimensional images using the interference of laser light beams.
(d) the name for an imaging process that occurs within a camera when a photograph is taken.
(e) the production of a two dimensional image of the three dimensional object.