Museum of Science and Industry

Three Colors of Light

See what happens when you mix together the three primary colors of light.

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Lesson at a Glance

Students will learn that the three primary colors of light are red, blue and green. They will learn that the primary colors of light combine to make white light, and will combine previously learned information about how our eyes function and the electromagnetic spectrum.

Illinois Learning Standards

Late Elementary
11: A, B; 12: C; 13: A
Middle / Junior High
11: A, B; 12: C; 13: A

Background Information

Look above you, toward the light. Light from the sun or a light bulb may appear colorless, but it is actually white light. Light that our eyes perceive to be whate is made from a combination of several colors.

Think of a prism. When you shine a light toward a prism, the white light is refracted, making all seven colors visible: red, orange, yellow, green, blue, indigo and violet. This is because each color has a different amount of energy. At one end of the spectrum, violet has a smaller wavelength and a higher frequency (meaning more energy), while at the other end red has a longer wavelength and lower frequency (meaning less energy).

When light waves with different frequencies are combined, the result is white light. The color "white" doesn't exist on the electromagnetic spectrum. Our eyes can be tricked into seeing white light by combining the three primary colors of light: red, blue and green. This is because of the anatomy of our eye. The cone cells in our eyes contain pigments that are sensitive to specific colors; we have one type of cone cell receptive to red light, one cone cell receptive to blue, and a third receptive to green. When our eyes are exposed to equal amounts of red, blue and green light, the cones absorb the wavelengths from each and tell our brains we are seeing white light.