5.53. Color http://www.ck12.org
pigment called chlorophyll, which is found in plants. Chlorophyll absorbs all but green wavelengths of visible light.
Pigments are also found in many manufactured products. They are used to color paints, inks, and dyes. Just three
pigments, called primary pigments, can be combined to produce all other colors. The primary colors of pigments
are the same as the secondary colors of light: cyan, magenta, and yellow.
Q:A color printer needs just three colors of ink to print all of the colors that we can see. Which colors are they?
A:The three colors of ink in a color printer are the three primary pigment colors: cyan, magenta, and yellow. These
three colors can be combined in different ratios to produce all other colors, so they are the only colors needed for
full-color printing.
Summary
- The wavelength of visible light determines the color that the light appears. Light with the longest wavelength
appears red, and light with the shortest wavelength appears violet. In between are the wavelengths of all the
other colors of light. - A prism separates visible light into its different colors. As light passes through the prism, it slows and bends,
but different wavelengths bend at different angles. This separates light into different wavelengths, forming a
rainbow of colors. - The wavelengths of visible light that an object reflects or transmits determine the color that the object appears
to the human eye. - The human eye can distinguish only red, green, and blue light. These three colors are the primary colors
of light. All other colors of light can be created by combining the primary colors. Secondary colors of
light—cyan, yellow, and magenta—form when two primary colors combine equally. - Pigments are substances that color materials by reflecting light of certain wavelengths and absorbing light of
other wavelengths. The primary pigment colors are cyan, yellow, and magenta. They can be combined to
produce all other colors.
Vocabulary
- pigment: Substance that colors materials by reflecting light of certain wavelengths and absorbing light of all
other wavelengths. - primary color: One of three colors of light (red, green, or blue) that can be combined to produce all other
colors of light.
Explore More
At the following URL, read about color addition and try the color addition widget. Then answer the Check Your
Understanding questions at the bottom of the Web page. Be sure to check your answers.
http://www.physicsclassroom.com/Class/light/u12l2d.cfm
Review
- What determines the color of visible light?
- Which color of light has the longest wavelength? Which color has the shortest wavelength?
- How does a prism separate visible light into its different colors?
- To a person with normal vision, the apple in theFigure5.119 appears green. Explain why.
- The human eye can detect only three colors of light. What three colors are they? How can we perceive other
colors of light?