CHAPTER 29 YEAH
Quiz yourself by thinking what should be in
each of the black spaces below before clicking
on it to display the answer.
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| What happens to light when it strikes a metal surface? | Almost all of the energy is
reflected back.
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| What happens to light when it strikes glass or water? | Some of the energy is reflected
and some is transmitted through
the glass or water.
Water: 2% is reflected
Glass: 4% is reflected
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| When light strikes a flat mirror at a certain angle, predict the path of the reflected light. | Reflects at the same angle but in
the opposite direction
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| .When you view your image in a plane mirror, how far behind the mirror is your image compared with your distance in front of the mirror? | Same distance behind the mirror
as the objecvt is in front.
Object distance = image
distance
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| Does the law of reflection hold for diffuse reflection? Explain. | Yes. Every individual ray folows
the law of reflection. But incident
rays hit many different-angled
surfaces which causes reflection in
many different direciton.
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| Contrast the reflection of light from a rough and a smooth surface. | r- Rays of light striking this
surface enounter many different
flat surfaces facing in all
directions so light rays are reflect
in many different directions.
S-Rays of light strike at all
the same angle and reflect at all the same direction
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| What is meant by the idea that a surface may be polished for some waves and rought for others? Give an example. | if the difference in elevations of the surface are less than 1/8 the
length of the light wave, the
surface is considered smooth.
Piece of paper is considered
smooth for a long radio wave,
but rought for a short light
wave.
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| What is the effect on sound when room surfaces are too reflective? Too absorbent? | Too reflective : garbled sound
Too absorbent: sound is dull and
lifeless.
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| What could an acoustical engineer do in designing a room to reduce the sound level? | Count use soft, absorbent
materials so that some of the
sound waves are absorbed.
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| How are reflection and refraction alike? How are they different? | A- when waves reach a
boundary of a new medium.Involve change in direction of a wave
D:Refl. occurs when the waves DONT go through the new medium but bounce back,
refr. when the wave go into new medium. Refr: waves chng spd, refl: waves
travel same
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| When a wave crosses a surface at an angle from one medium into another, why does it “pivot” as it moves across the boundary into the new medium? | Wave pivots because the part of
the wave that reaches the news
medium first changes speed while
the rest of the wave does not.
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| What is the orientation of a ray in relation to the wave front of a wave | A ray is perpendicular to the wave front
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| Why do sounds carry across a lake better at night than during the day? | Air near the ground is colder than
the air above, so speed of sound is
slower near the ground and faster
in the warm air above causing the
sound waves to bend toward the
ground.
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| What are 3 examples of the effect of refraction that we can see? | Stars twinkle
Pencil appear bent in water
Air above a hot stove appears
to shimmer
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| What are 3 conditions that could cause refraction | Light waves change speed
(refract) when light passes
From one medium to another
Through different
temperatures of the same
medium
Through different densities of
the same medium.
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| Does refraction occur for both sound waves and light waves? | yes
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| If light had the same speed in air and in water, would light be refracted in passing from air into water? Explain | No because refraction is caused by
change in speed so
No change in speed = no
refraction
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| If you can see the face of a friend who is underwater, can she also see you? Why? | Yes because the light paths are
reversible for reflection and
refraction.
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| . Does refraction tend to make objects submerged in water seem shallower or deeper than they really are? | Shallower
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| What happens to the speed of light as it goes from air to water? Air water: light shows down Which way does light bend as it passes from air to water? | Air water: light shows down
Air water: light bends toward
the normalAir water: light bends toward
the normal
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| As light passes through glass or water, do the high or low frequencies of light interact more in the process of absorption and reemission and, therefore, slow down more? | High frequencies – b/c/ they are
closer to the natural frequency of
glass and water and, therefore,
resonate more.
More interaction = slower speed
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| Why does blue light refract at greater angles than red light in transparent materials? | Blue light (higher frequency)
refracts (bends) more because it
slows down more than red light.
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| Describe the conditions necessary for a motorist to see a mirage. | The air near the surface must be
very hot – light speeds up in the
hot air and refracts upward.
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| Explain how a prism separates white light into colors. Include a diagram to illustrate your answer | Blue light slows down more than
red so blue light is bent more than
red. When this happens twice (at
the two nonparallel glass surfaces
of a prism) the effect is enough to
see the rays dispersed
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| Describe the sky conditions necessary for a rainbow. Where must you be to see the rainbow? | Sun must be shining in one part of
the sky and water droplets from a
cloud or falling rain in the
opposite part of the sky.
You must be standing with your
back to the sun.
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| What are two factors that cause a diamond to “sparkle” and produce brilliant colors? | . Small critical angle of
diamonds (24.6
o
)
2.Unusually low speed of light
in diamonds (0.4 c)
These two factors cause light to be
dispersed in a broad, intense
sparkle
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| Compare the critical angles of water, glass and diamonds |
Water – 48
o
Glass -- 43
o
Diamonds – 24.6
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| How much light leaves a medium if it strikes the boundary at an angle greater than the critical angle? | none
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| Give 3 specific examples of uses for optical fibers. | Mechanics use them to look inside
engines.
Physicians used them to look
inside a patient’s body.
Communications: replace copper
telephone wires and underseas
cables (more information can be
carried on by high frquency light
than by low freq
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Created by:
Kachaj