Page 432 - Schaum's Outline of Theory and Problems of Applied Physics

CHAP. 33] PHYSICAL AND QUANTUM OPTICS 417

33.8. When light is directed at a metal surface, upon what property of the light does the maximum energy of the emitted
electrons depend?

33.9. The pupils of a person’s eyes in ordinary light are about 3 mm in diameter, and for most people the distance of
most distinct vision is about 25 cm. Find the resolving power of the eye under these circumstances in green light
of wavelength 5.5 × 10 −7 m. (In fact, the photoreceptors in the retina are not quite close enough together to permit
such sharp vision, and 0.1 mm is a more realistic resolving power.)

33.10. A radar whose operating frequency is 9000 mHz has an antenna 1.5 m wide. What is its resolving power at a range
of 5 km?

33.11. A telescope has an objective lens 10 cm in diameter. What is the maximum distance at which the telescope can
resolve two objects 1 cm apart? Assume that λ = 5 × 10 −7 m.

2
33.12. Light from the sun arrives at the earth at the rate of about 1400 W/m of area perpendicular to the direction of the
light. Assuming that sunlight consists exclusively of light of wavelength 6 × 10 −7 m, find the number of photons
per second that fall on each square meter of the earth’s surface directly facing the sun.

33.13. How many photons per second are emitted by a 50-kW radio transmitter that operates at a frequency of
1200 kHz?

19
33.14. What is the operating voltage of an X-ray tube that produces X-rays of frequency 10 Hz?
33.15. Find the wavelength of the X-rays produced by a 50,000-V X-ray machine.

33.16. The work needed to remove an electron from the surface of sodium is 2.3 eV. Find the maximum wavelength of light
that will cause photoelectrons to be emitted from sodium.

15
33.17. Photoelectrons are emitted by a copper surface only when light whose frequency is 1.1×10 Hz or more is directed at
15
it. What is the maximum energy of the photoelectrons when light of frequency 15×10 Hz is directed at the surface?
6
33.18. What is the kinetic energy in electronvolts of a proton (m = 1.67 × 10 −27 kg) whose velocity is 5 × 10 m/s?
33.19. Find the velocity of a 50-eV electron.

Answers to Multiple-Choice Questions

33.1. (a), (b), (c) 33.6. (c)

33.2. (a) 33.7. (d)

33.3. (b) 33.8. (a)
33.4. (a) 33.9. (c)

33.5. (a) 33.10. (c)

Answers to Supplementary Problems

33.1. Polarization

33.2. Polarization