| Question | Answer |
| What happens to
light when it strikes
a metal surface? | Almost all of the energy is
reflected back. |
| 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 |
| 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 |
| .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 |
| 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. |
| 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 |
| 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. |
| 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. |
| 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. |
| 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 |
| 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. |
| What is the
orientation of a ray
in relation to the
wave front of a
wave | A ray is perpendicular to the wave front |
| 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. |
| 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 |
| 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. |
| Does refraction
occur for both sound
waves and light waves? | yes |
| 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 |
| 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. |
| . Does refraction
tend to make objects
submerged in water
seem shallower or
deeper than they
really are? | Shallower |
| 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 |
| 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 |
| 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. |
| 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. |
| 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 |
| 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. |
| 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 |
| Compare the
critical angles of
water, glass and
diamonds | Water – 48
o
Glass -- 43
o
Diamonds – 24.6 |
| How much light
leaves a medium if it strikes the boundary
at an angle greater
than the critical
angle? | none |
| 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 |
