Download Light and Color

Physics: Form WS9.1.1A
Name ______________________________
LIGHT
Date _________________ Period _____
Light and Color
The sun shines brightly. Green leaves wave in a gentle breeze.
Suddenly there is a cloudburst. As quickly as the rain came, it is
gone, followed by a beautiful rainbow. What is all this color
about? Color comes from light, an electromagnetic wave that
travels in straight lines in all directions from a light source
through both space and objects. Matter usually does not produce
light, rather, it is reflected, absorbed, or passes through matter.
What happens to light when it strikes matter depends on the
material of which the matter is composed. All matter reflects and
absorbs some light. Materials through which no light passes,
such as wood or brick, are opaque. Materials that only let some
light pass, such as waxed paper or frosted glass are translucent.
Materials through which most light passes, such as glass, are
transparent. Light often seems pretty colorless, but sunlight and
electric lights contain a mixture of frequencies. The color of an
object depends on which frequencies are reflected and which are
absorbed. The green leaves waving in the breeze reflect green
light and absorb all the other frequencies. We interpret light based on the way we see it. The three primary colors
of light are red, blue, and green. Light that appears to be any color can be made with different mixtures of the three
primary colors of light. White light is a mixture of all three. Mixing pigments is different than mixing light because
the appearance of pigments is based on the colors of light they absorb and reflect. Primary pigment colors result
from absorption of a primary color of light. The three primary colors of pigments are cyan, magenta, and yellow.
Cyan absorbs red, and reflects blue and green. Magenta absorbs green, and reflects red and blue. Yellow absorbs
blue, and reflects red and green. A pigment of any color can be made with different mixtures of the three primary
colors of pigments. But a mixture of all three pigments is not white, because it is absorbing all the primary colors.
Instead, it is grey or black.
Answer the questions below based on the reading above and on your knowledge of physics.
1. How are opaque, translucent, and transparent matter similar? How are they different?
2. What happens when light strikes an opaque green object such as a leaf?
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Physics: Form WS9.1.1A
Light and Color
LIGHT
Page 2
3. What are the primary colors:
a. of light?
b. of pigment?
4. How are primary colors of light and primary colors of pigments similar? How are they different?
5. A mixture of the three primary colors of light appears bright and colorless (white light), but a mixture of the
three primary pigments appears dark. Why?
6. Refer to the diagram below showing the primary colors of light and the results of their mixing to answer the
following about what color you see under the following conditions:
a. Red light is absorbed.
b. Red light is reflected.
c. Blue and green light are absorbed.
d. Blue and green light are reflected.
e. Green light is absorbed.
f. Blue light is absorbed.
g. Red, blue, and green light are reflected.
h. Red, blue, and green light are absorbed.
7. What colors of light energy do green plants use for photosynthesis? Explain.
© Evan P. Silberstein, 2014