Ch 28: Color Review
1. How did Isaac Newton show that sunlight is composed of a mixture of all colors of the rainbow?
By passing a narrow beam of sunlight through a triangular-shaped glass prism, Newton showed that
sunlight is composed of a mixture of all the colors of the rainbow.
2. What determines the color of an opaque object?
The color of an opaque object is the color of the light it reflects.
3. When green light shines on a red rose, why do the petals look black?
Answer: The petals absorb rather than reflect the green light. So, the rose appears to have no color
at all—black.
4. What determines the color of a transparent object?
The color of a transparent object is the color of the light it transmits.
5. Which visible frequencies make up the brightest part of sunlight?
Yellow-green light is the brightest part of sunlight.
6. Which three visible frequencies combine to form almost any color?
You can make almost any color at all by overlapping red, green, and blue light and adjusting the
brightness of each color of light.
7. What color does red light plus blue light make?
Answer: Magenta
8. What happens when you combine any color with its complementary color?
Every color has some complementary color that when added to it will produce white.
9. What color does white light minus yellow light appear?
Answer: Blue
10. Which visible frequencies are absorbed by a mixture of paints or dyes?
When paints or dyes are mixed, the mixture absorbs all the frequencies each paint or dye absorbs.
11. Why is the sky blue?
The sky is blue because its component particles scatter high-frequency light.
12. Why are sunsets red?
By the time a beam of light gets to the ground at sunset, all of the high-frequency light has already
been scattered. Only the lower frequencies remain, resulting in a red sunset.
13. If molecules in the sky scattered low-frequency light more than high-frequency light, how would the colors of
the sky and sunsets appear?
Answer: If low frequencies were scattered more, red light would be scattered out of the sunlight on
its long path through the atmosphere at sunset, and the sunlight to reach your eye would be
predominantly blue and violet.
14. What happens to an excited atom after it emits light?
After an excited atom emits light, it returns to its normal state.
Multiple Choice
1. Black is
a.
b.
c.
d.
a combination of all the colors of the spectrum.
a combination of two or more appropriate colors.
light when a prism is held upside down.
the absence of light.
Answer: D
2. To say that rose petals are red is to say that they
a. absorb red.
b. reflect red.
c. emit red.
d. transmit red.
Answer: B
3. The color light that gets through a piece of transparent blue glass is
a. blue.
b. yellow, the opposite color of blue.
c. actually green.
d. red minus magenta.
Answer: A
5. When red and blue light are overlapped, the color produced is
a. magenta.
b. yellow.
c. cyan.
d. white.
Answer: A
6. The complementary color of blue is
a. magenta.
b. yellow.
c. cyan.
d. white.
Answer: B
7. For mixing pigments or dyes, the primary colors are magenta, cyan, and
a. red.
b. green.
c. yellow.
d. blue.
Answer: C
8. The blueness of the daytime sky is due mostly to light
a. absorption.
b. transmission.
c. reflection.
d. scattering.
Answer: D
9. The redness of a sunrise or sunset is due mostly to light that has not been
a. absorbed.
b. transmitted.
c. scattered.
d. polarized.
Answer: C
11. The frequency of an emitted photon is related to its
a. amplitude.
b. polarization.
c. momentum.
d. energy.
Answer: D
12. Combining red and green light (with equal intensity) makes ____ light; combining red and blue light (with
equal intensity) makes ____ light; and combining blue and green light (with equal intensity) makes ____
light. Choose the three colors in respective order.
a. brown, purple, aqua
b. brown, magenta, yellow
c. yellow, magenta, brown
d. yellow, magenta, cyan
Answer: D
13. Demonstrate your understanding of color subtraction by completing the following color equations. Select
colors from the Color Table at the right.
a. White - Blue = _____
b. White - Red = _____
c. White - Green = _____
d. White - Blue - Green = _____
e. White - Yellow = _____
f. Red + Green - Green = _____
g. Yellow - Green = _____
Answer: See table above.
a. White - Blue = R+G+B - B = R+G = Yellow
b. White - Red = R+B+G - R = G+B = cyan
c. White - Green = R+G+B - G = R+B = magenta
d. White - Blue - Green = R+G+B - B - G = R = red
e. White - Yellow = R+G+B - R+G = B = blue
f. Red + Green - Green = R + G - G = R = red
g. Yellow - Green = R+G - G = R = red (Note the similarity to part f.)
14. Express your understanding of filters by answering the following questions.
a. A red filter is capable of transmitting ____ light (if it is incident upon the filter).
b. A blue filter is capable of transmitting ____ light (if it is incident upon the filter).
c. A green filter is capable of transmitting ____ light (if it is incident upon the filter).
d. A red filter will absorb ____ light (if it is incident upon the filter).
e. A blue filter will absorb ____ light (if it is incident upon the filter).
f. A yellow filter will absorb ____ light (if it is incident upon the filter).
g. A magenta filter will absorb ____ light (if it is incident upon the filter).
Answer: See sentences above.
a. Red filters absorb cyan light (the complementary color of red). If white light (red + blue + green) shines on a red
filter and cyan (blue + green) light is absorbed, all that is left to be transmitted is red light.
b. Blue filters absorb yellow light (the complementary color of blue). If white light (red + blue + green) shines on a
blue filter and yellow (red + green) light is absorbed, all that is left to be transmitted is blue light.
c. Green filters absorb magenta light (the complementary color of green). If white light (red + blue + green) shines on
a green filter and magenta (red + blue) light is absorbed, all that is left to be transmitted is green light.
d. Red filters absorb its complementary color - cyan. So this question could be answered as cyan. And since cyan
light consists of blue + green light, this question could also be answered as blue + green.
e. Blue filters absorb its complementary color - yellow. So this question could be answered as yellow. And since
yellow light consists of red + green light, this question could also be answered as red + green.
f. Yellow filters absorb its complementary color - blue. So this question must be answered as blue.
g. Magenta filters absorb its complementary color - green. So this question must be answered as green.