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16.1 The Nature of Light
1. You can often see some of the details in the dark portion
of a crescent moon. Where does the light come from that allows
you to see this?
2. Newton thought light was a stream of particles at about
the same time that Huygens thought light was a wave. Most people
accepted Newton's ideas of light and ignored Huygens' ideas. Why
might that have been?
3. After Thomas Young's famous double-slit experiment,
people regarded light as a wave. What made Young's ideas about
light different-and more compelling-than Huygens' ideas?
4. If white is the presence of all colors, what is black?
16.2 The Speed of Light
5. Explain why the lightning and thunder of a summer's
storm show that the speed of light is greater than the speed of
sound?
6. Light and television or radio waves are all electromagnetic
waves and travel with the same speed. Television often uses communications
satellites that orbit about 35,000 km above Earth's surface. How
can this explain the lag sometimes seen as a TV interviewer talks
with someone at a remote location?
16.3 Reflection
7. Make a sketch of how you could arrange two mirrors to
make a periscope that would allow you to see over taller people
in a crowd or to see around a corner.
8. Shine a thin beam of light on a mirror and look at the
reflected beam. If you now rotate the mirror though some angle,
you will find the reflected beam to be rotated through twice that
angle. Draw a diagram that shows why this happens.
9. What evidence can you think of that shows the frequency
of light is not affected by reflection?
16.4 Refraction
10. Is light bent toward or away from the normal as it
passes from ethyl alcohol (n = 1.36) into glass (n = 1.55)?
11. Is light bent toward or away from the normal as it
passes from ethyl alcohol (n = 1.36) into olive oil (n = 1.46)?
12. What evidence can you think of that shows the frequency
of light is not affected by reflection?
16.5 Total Internal Reflection
13. Is light bent toward or away from the normal as it
passes from ethyl alcohol (n = 1.36) into air (n = 1.00)?
14. Is light bent toward or away from the normal as it
passes from olive oil (n = 1.46) into water (n = 1.33)?
15. Make a sketch of how you could arrange two prisms to
make a periscope that would allow you to see over taller people
in a crowd or to see around a corner.
16. As light is reflected and bounces around a single fiber
optic, it becomes all jumbled up. A single fiber optic-or "light
pipe"-will not produce a clear image. How, then, can a clear
image be seen?
16.6 Polarization
17. If you hold onto the end of a rope and wiggle it up
and down you produce a continuous wave that is polarized vertically.
You can continue to do this until your arm gets tired. Yet the
light from a flashlight is not polarized. Why not?
18. Consider the polarizer and analyzer sketched in Figure
16.24. Describe the intensity of the light passing through the
analyzer as the analyzer is rotated a full 360.
19. Glasses for color 3-D movies usually have polarizing
lenses-one lens with its polarization axis vertical and one lens
with its polarization axis horizontal. How can this produce a
3-D image?
20. Consider light that has passed through a Polaroid sheet.
If a second Polaroid sheet, used as an analyzer as in Figure 16.24,
initially aligned to allow maximum light to pass through it, is
now rotated until the light passing through it is a minimum (or
zero), through what angle has the second Polaroid sheet been rotated?
21. Consider the arrangement of polarizer and analyzer
shown in Figure 16.24. Align the polarizer and analyzer so that
maximum light passes the analyzer. Now insert a third Polaroid
sheet between the two. Describe what happens-how much light passes
through the entire system-as the third and inner Polaroid sheet
is rotated a full 360.
22. Consider the arrangement of polarizer and analyzer
shown in Figure 16.24. Cross the polarizer and analyzer 90 so
that no light passes the analyzer. Now insert a third Polaroid
sheet between the two. Describe what happens-how much light passes
through the entire system-as the third and inner Polaroid sheet
is rotated a full 360.
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