Remember that two factors affect an object’s color. One is the wave-
lengths present in the light that shines on the object. The other is the
wavelengths that the object’s material reflects or absorbs. Materials
can be mixed to produce colors just as light can. Materials that are
used to produce colors are called pigments. The
are cyan, yellow, and magenta. You
can mix primary pigments just as
you can mix primary colors to
produce all the colors.
The primary pigment colors are
the same as the secondary colors of
light. The secondary pigment colors
are red, blue, and green—the same
as the primary colors of light.
The effect of mixing pigments
is different from the effect of mixing
light. Remember that a colored
material absorbs all wavelengths
except those of the color it reflects.
Ye llow paint absorbs all wavelengths
except yellow. Because pigments
absorb wavelengths, whenever you
mix pigments, you are subtracting
wavelengths rather than adding them. Mixing colors by subtracting
wavelengths is called subtractive color mixing. When all three primary
pigments are mixed together in equal amounts, all wavelengths are
subtracted. The result is black—the absence of reflected light.
check your reading How is mixing pigments different from mixing light?
Chapter 17: Electromagnetic Waves 579
1. What are some ways in
which materials affect how
light is transmitted?
2. How does a polarizing filter
3. In order for an object to
appear white, which wave-
lengths must the light contain
and the object reflect?
4. Apply Imagine that you are a
firefighter searching a smoke-
filled apartment. Would using
a stronger light help you see
better? Explain your answer.
5. Predict Higher-energy EM
waves penetrate farthest into a
dense medium. What colors
are more likely to penetrate to
the bottom of a lake?
6. Synthesize If you focus a red
light, a green light, and a blue
light on the same part of a
black curtain, what color will
the curtain appear to be? Why?
The inks used to make the
circles on this page are
They combine to make
the secondary pigments
red, blue, and green.