Physics 1010

Question Set 13A

Review Questions: Properties of Light

Answers


1. Most of the electromagnetic spectrum consists of visible light.

A. True
B. False

2. Electromagnetic waves consist of

A. compressions and rarefactions of electromagnetic pulses.
B. oscillating electric and magnetic fields.
C. particles of light energy.
D. high-frequency gravitational waves.

3. The source of all electromagnetic waves is

A. changes in atomic energy levels.
B. vibrating atoms.
C. accelerating electric charges.
D. crystalline fluctuations.
E. all of these.

Reasoning: An accelerated charge produces electromagnetic waves.

4. Electromagnetic waves

A. can travel through a vacuum.
B. need a medium to travel through.

Reasoning: Unlike sound waves, EM waves are not mechanical waves, thus they do not need a medium to travel.

5. The main difference between a radio wave and a light wave is its

A. speed.
B. wavelength.
C. frequency.
D. all of these.
E. two of these.

Reasoning: Wavelength and frequency

6. The speed of light in glass compared to the speed of light in a vacuum is,

A.100 % faster.
B. 100 times slower.
C. 50 % faster.
D. 33 % slower.

7. Which of these electromagnetic waves has the shortest wavelength?

A. radio waves
B. infrared waves
C. X-rays
D. ultraviolet waves
E. light waves

8. Compared to radio waves, the velocity of visible light waves in a vacuum is

A. less.
B. more.
C. the same.

9. If an electron vibrates up and down 1000 times each second, it generates an electromagnetic wave having a

A. period of 1000 s.
B. speed of 1000 m/s.
C. wavelength of 1000 m.
D. frequency of 1000 Hz.
E. wavelength of 1000 km.

10 . Which of the following is fundamentally different from the others?

A. sound waves
B. X-rays
C. gamma rays
D. light waves
E. radio waves

Reasoning: Sound waves are mechanical waves. The rest of the answers are EM waves which are NOT mechanical waves.

11. The natural frequency of the atoms in glass is in the

A. Radiowave part of the spectrum.
B. visible part of the spectrum.
C. ultraviolet and infrared part of the spectrum.

Reasoning: See page 501 (last paragraph discusses this issue).

12. When ultraviolet light is incident upon glass, atoms in the glass

A. are forced into vibration.
B. resonate.
C. pass the light energy along practically undiminished.
D. freely absorb and re-emit most of the ultraviolet light.

Reasoning: See page 500.

13. When visible light is incident upon clear glass, atoms in the glass

A. are forced into vibration.
B. resonate.
C. convert the light energy into internal energy.

14. Consider light energy that is momentarily absorbed in glass and then re-emitted. Compared to the absorbed light, the frequency of the re-emitted light is

A. considerably less.
B. slightly less.
C. the same.
D. slightly more.
E. considerably more

Reasoning: See page 501 (1st paragraph has some discussion about this.)

15. Compared to its average speed in air, the average speed of a beam of light in glass is

A. more.
B. less.
C. the same.

16. Infrared waves are often called heat waves because they

A. emanate from relatively hot sources.
B. consist of frequencies lower than those of visible light.
C. induce resonance in molecules and increase internal energy in a substance.
D. are the predominant waves emitted by the sun

17. Sunburns are produced by

A. ultraviolet light.
B. visible light.
C. infrared light.
D. all of these.
E. none of these.

18. The Earth's atmosphere is transparent to most waves in the

A. entire infrared part of the spectrum.
B. visible part of the spectrum.
C. all of the ultraviolet part of the spectrum.
D. entire electromagnetic spectrum.

19. The sensation of color is seen when light falls on the eye's

A. rods.
B. cones.
C. both.
D. neither.

20. The cones in the retina of the eye are

A. most densely packed at the center of vision.
B. uniformly spread along the visual field.
C. concentrated along the periphery of vision.

21. Red-hot and blue-hot stars appear white to the eye because

A. the eye has difficulty seeing color at night.
B. they are too dim to fire the cones.
C. hey are too dim to fire the rods.
D. they are overwhelmed by the blackness of the nighttime sky.
E. eye receptivity peaks in the yellow-green part of the spectrum.

22. In the periphery of our vision, we are

A. more sensitive to low frequencies than high ones.
B. insensitive to color and movement.
C. sensitive to movement, but cannot see color.
D. sensitive to both movement and color.
E. none of these.

23. Color is seen by

A. the rods in the eye.
B. the cones in the eye.
C. both of these.
D. neither of these.

24. Information-carrying nerves are connected to the retina at

A. the fovea.
B. the blind spot.
C. the cornea.
D. the iris.
E. the periphery.

25. Things seen by moonlight usually aren't colored because moonlight

A. doesn't have very many colors in it.
B. is too dim to activate the retina's cones.
C. photons don't have enough energy to activate the retina's cones.
D. all of these.
E. none of these.