ID:______NAME:______________________________________DATE:___________________CLASS:______
Ch. 28 - Color…Do not lose this! No extra copies!
READ the information in the BOXES (and use the last POGILs) to answer the following questions:
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Visible Light is only thing we see.
White light contains the color spectrum ( ROY G BIV acronym)
o You see proof of this with a PRISM (more on that later!)
 White is not a color…it is the PRESENCE of all frequencies of visible light.
 Black is not a color – it is the ABSENCE of all frequencies of visible light. Objects appear black when they
absorb all frequencies of light incident upon them
o We see “white” when an object reflects the frequencies (ROYGBIV) of visible white light.
o We see “black” when an object absorbs all the frequencies of visible light incident upon it.
 The color of an OPAQUE object is the color of the light it reflects.
The square on the left reflects all the colors of light illuminating it.
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In sunlight (white light) it is white.
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When illuminated with blue light, it is blue.
The square on the right absorbs all the colors illuminating it.
 In sunlight it is warmer than the white square.
 When light is incident upon (SHINES ON) a surface, it is either reflected, absorbed, or transmitted.
o Usually, a combination of all 3 occurs (for example – visible light is both reflected and transmitted
through glass in a window – this is why you can see through glass but you can also see your reflection.
However, a slight amount is absorbed – this is why the window feels warm – that absorbed light is
converted to heat.)
 Most of the objects around us reflect rather than emit light. They reflect only part of the light that is incident
(shining) upon them, the part that gives them their color. A rose, for example, doesn't emit light; it reflects the
RED frequencies of visible light and absorbs the rest
1. Newton was the first person to make a systematic study of color. He allowed sunlight to pass through a prism, creating a
patch of colors on white paper called a ____________________________________________________.
2. Sunlight is an example of white light. Under white light, white objects appear ______________________ and colored
objects appear ________________________________________________________________________________________
3. Are the colors of the spectrum a property of white light or a prism itself?___________________________________
4. TRUE OR FALSE: Black objects that you can see do not absorb all light that falls on them. Explain:
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5. Why do you think your pupils appear black? _________________________________________________________________
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6. Very big particles, such as droplets of water, absorb more radiation than they scatter. How does this fact help to explain
why rain clouds appear dark?____________________________________________________________________________
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The colors of most objects around you are due to the way they reflect light.
Most materials absorb light of some frequencies and reflect the rest.
If a material absorbs white light of most frequencies and reflects red, then it appears red in white light.
It is important to note that an object can reflect only light of frequencies present in the illuminating
light.
The appearance of a colored object therefore depends on the kind of light used.
An incandescent light bulb (NOT the energy efficient bulbs, but the plain old filament and glass bulbs) emits
light of all the visible frequencies, but is richer toward the lower frequencies, therefore enhancing the reds.
The perceived color of an object is subjective (subject to change/vary from person to person) and depends on
the light source, although color differences between the objects are most easily detected in bright sunlight.)
7. Picture this – imagine you are wearing a white tee shirt in a room lit only by candle light. Then, you move to a room lit only
by fluorescent light bulbs.
a) In which room does your shirt appear to have more of a yellowish tint? _________________
b) In which room does your shirt appear to have more of a blue-ish/purple-ish tint? _______________________________
8. Look at your answer to #8. Do you think a candle is deficient (aka lacking) in higher or lower frequencies? WHY?
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9. Look at your answer to #8. Do you think a fluorescent light is richer in higher or lower frequencies? WHY?
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10.
In a dress shop that has only fluorescent lighting, a customer insists on taking a garment into the daylight at the
doorway. Is she being reasonable? Explain. (*hint – ladies, have you ever used a lit makeup mirror instead of the lighting in
your bathroom? Why?*)
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The color of a transparent object depends on the color of the light it transmits.
A piece of clear glass does not distort the image on the other side because all of the frequencies of visible
light can pass through
A blue piece of glass appears blue because it absorbs all the colors that compose white light, except blue,
which it transmits
The material in the transparent object that selectively absorbs colored light is known as a pigment.
o The energy of the absorbed light increases the KE of the atoms in the material, and the material is
warmed.
o Ordinary glass is transparent because it transmits white light of all visible frequencies equally well.
11.
White light shines on ordinary window glass. What color frequencies of the visible white light are transmitted
through the glass?
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12.
White light shines on a piece of red glass.
a) What color frequencies are TRANSMITTED?______________ ______________________________________________
b) What color frequencies are absorbed?_____________________________________________________________________
White light from the sun is a composite of ALL the visible frequencies. Sunlight’s radiation curve is shown below;
it is a graph of brightness versus frequency.
13.
14.
15.
16.
17.
What frequency of visible light on sunlight’s radiation curve has the highest frequency?_______ _____ _______
What frequency of visible light on sunlight’s radiation curve is the brightest?______________________________
Is the BRIGHTEST color also the HIGHEST FREQUENCY? (yes/no)________________________
Do you think our eyes are more sensitive to high BRIGHTNESS or high FREQUENCY?________________________
What is the color of common tennis balls (and fast pitch softballs), and why?
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18.
Why do you think some traditional red fire engines are being replaced by neon yellow-green engines?
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MIXING COLORED PIGMENTS
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Paints and dyes contain finely divided solid particles of pigment that produce their colors by absorbing
light of certain frequencies and reflecting light of other frequencies
o You SEE the light that is reflected.
o This is called color mixing by subtraction, because the pigments absorb (or subtract) certain
frequencies of light.
 When a frequency of light is reflected, you SEE it.
 When a frequency of light is absorbed, it transforms into HEAT
o The subtractive primary colors are magenta, yellow, and cyan.
19.
Shine red light on a red rose. Why will the temperature of the GREEN leaves increase more than the
temperature of the red petals?
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20.
When green light shines on a red rose, why do the petals look black?
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MIXING COLORED PIGMENTS
Paints and dyes contain finely divided solid particles of pigment that produce their colors by absorbing
light of certain frequencies and reflecting light of other frequencies
o You SEE the light that is reflected.
o This is called color mixing by subtraction, because the pigments absorb (or subtract) certain
frequencies of light.
 When a frequency of light is reflected, you SEE it.
 When a frequency of light is absorbed, it transforms into HEAT
o The subtractive primary colors are magenta, yellow, and cyan.
21.
Use your common sense and think back to your pre-school finger painting days…if you mix red, blue,
and green paint, what color do you see?
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22.
What two pigments mixed together will reflect red?
23.
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What two pigments mixed together will reflect green?
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24.
A spotlight is coated so that it won’t transmit blue from its white-hot filament. What color is the
emerging beam of light?
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25.
How could you use the spotlights at a play to make the yellow clothes of the performers suddenly
change to black?
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26.
What colors of ink do color ink-jet printers use to produce the colors you see? How does this relate to
what you learned?
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Want extra practice on this topic? Go to
http://www.physicsclassroom.com/Class/light/U12l2e.cfm, scroll through, read,
and complete the online questions and answers!
READ 28.10 Why Water Is Greenish Blue for these questions….
27.
a)
Is the following sentence true or false? The deep-blue color of a pond or an ocean is due to the color of the water
itself.__________________________________
EXPLAIN:
28. Is the following sentence true or false? Shallow water is transparent to nearly all the frequencies of white light._________
a) EXPLAIN:
29. Circle the letter of the color(s) that water molecules absorb; assume the water is deeper than 15 m.
a. red
b. green
c. blue
d. all
30.
The only light to reach very far beneath the surface of the ocean is greenish blue. Objects at these depths either reflect
greenish blue of reflect no color at all. If a ship that is painted red, green, and white sinks to the bottom of the ocean, how will
these colors appear?
a. Red will appear____________________________
b. Green will appear __________________________
c. White will appear___________________________
31.
Why do you think lobsters and crabs (bottom dwelling creatures) are red? Explain using light and color concepts:
32.
Try Doing Physics page 429. What did you observe? ___________________
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Check #the previous questions in your textbook – p. 435-437
**As always…please see a teacher for any additional clarification you need!!!**
Refraction occurs when the average speed of light changes in going from one
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transparent medium to another.
o We can understand this by considering the action of a pair of toy
cartwheels connected to an axle as the wheels roll gently downhill from a
smooth sidewalk onto a grass lawn.
o If the wheels meet the grass at some angle, they will be deflected from
their straight-line course. The direction of the rolling wheels is shown by
the dashed line.
o Note that on meeting the lawn, where the wheels roll more slowly owing to
interaction with the grass, the left wheel (YOUR left) slows down first. This
is because it meets the grass while the right wheel (YOUR right) is still on
the smooth sidewalk.
o The faster-moving right wheel tends to pivot about the slower-moving left
wheel because during the same time interval, the right wheel travels farther than the left one.
33.
How does the above analogy help explain how light “slows down” when it passes through a material,
compared to passing through a vacuum?
The refraction of light is responsible for many illusions; one of them is the apparent bending of a stick partly immersed in
water.
 The submerged part seems closer to the surface than it really is.
 Likewise when you view a fish in the water. The fish appears nearer
to the surface and closer.
 Because of refraction, submerged objects appear to be magnified. If
we look straight down into water, an object submerged 4 meters
beneath the surface will appear to be 3 meters deep.
34.
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Using the images in both of the above boxes, does light travel faster in AIR or in WATER? EXPLAIN
Recall from Chapter 27 that when light RESONATES with a transparent medium, it is absorbed (**UV light is
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absorbed by glass because its frequency matches the natural frequency
of glass**)
And light with frequencies near the resonant frequencies interacts more
often therefore travels more slowly.
Since the natural or resonant frequency of most transparent materials is
in the ultraviolet part of the spectrum, higher-frequency light travels more
slowly than lower-frequency light.
Violet light travels about 1% slower in ordinary glass than red light. Light
waves with colors between red and violet travel at their own intermediate
speeds.
This separation of light into colors is called dispersion.
35.
Does the RED light or BLUE light in the above image travel more slowly through the prism? EXPLAIN
36.
Does a prism CHANGE white light into colors, or SEPARATE white light into colors? Explain!
REFLECTION:
Rule for reflection:
You can see your
perfect reflection when
all of the reflected light
rays are parallel to
each other, just like the
incident (initial) light
rays are parallel to
each other.
look at the diagrams 
37. The RULE for reflection differs from the LAW of reflection. (see above)
a) The Law of Reflection still holds true for “diffuse reflection.” Why, then, can you not see your reflection when
looking into a piece of paper?
b) Why CAN you see your reflection when looking into a mirror?
38.
Does glass transmit ALL of the visible light that is incident upon it? Why or Why not? (Use common sense!!!
Look at OUR classroom windows!) If not, what happens to the light that is not transmitted?
39.
How do you think security mirrors work (those window – mirrors that are in interrogation rooms)? Are
they transparent? Reflective? Both? Think, discuss, google, learn:
40.
Make-up mirrors can magnify your image. Do you think that these mirrors are FLAT, CONCAVE, or CONVEX? Explain why:
______
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41.
You may see the following on a side view mirror of a car: WARNING: OBJECTS IN MIRROR MAY BE CLOSER THAN THEY
APPEAR. Do you think that the side view mirrors are FLAT, CONCAVE, or CONVEX? Explain why:
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Here is a diagram showing “Mirage.” The arrows show the direction of
the reflected light.
42.
When you saw Mirage, you saw a pig. Pretend the circular “dots” in the below
diagram are the “pig.” How does mirage work (in your own words?)
Read ALL of Ch 28 to determine why sunsets are red, etc. Won’t
be assessed on it, but it will help explain a lot of what you see in
everyday life! Plus, it will help you sound smart in conversations 
43.