The Colors of Light

Students will explore illuminating different objects with different colors of light.

Lab Summary

Determine what colors result from adding various primary colors of light. Explore the effects of illuminating different objects with different colors of light.

Objects that we see can be broadly grouped into two categories: luminous and illuminated. Luminous objects such as the sun generate their own light -- in the case of the sun and other stars, the light is a result of nuclear reactions taking place within the sun. The vast majority of objects we see, however, are illuminated -- that is, they are capable of reflecting light rays to our eyes, but do not generate these light rays themselves.

The colors that we see depend on the wavelength and frequency of light energy that the object reflects to our eyes. The lowest frequency humans perceive appears as red (650-750 nm wavelength), and the highest frequency appears violet (390-430 nm wavelength). Within this range is the traditional grouping of the colors of the rainbow ("Roy G. Biv"): red, orange, yellow, green, blue, indigo and violet. Most objects reflect only part of the light spectrum: a yellow pencil reflects the yellow part of the visible spectrum only. Scientists still do not fully understand how the molecular structure of objects causes them to be able to reflect only certain frequencies of visible light.

Hypothesize: If sunlight is reflected from so many objects in so many different ways, what colors of light could sunlight be made of? Can you devise a simple experiment to test your answer? In the activity that follows, you will be asked to predict the results of combining various colors of light, and you will get a chance to see how objects' appearances change in different colors of light.

Published: March 2003

Downloads

• The Colors of Light (46 KB, .zip)

  Includes experiment setup and procedures

Here's What You Need

U.S. Educator prices shown.

Basic Optics Light Source (OS-8470) - $119

An all-in-one bright point source, illuminated crossed-arrow object, primary-color source, and ray box with up to five parallel rays.

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Ray Optics Kit (OS-8516A) - $60

A basic set of lenses and mirrors for ray and color experiments.

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Other Materials

• Colored construction paper: red, yellow, green, blue
• Optional: additional colors of construction paper or additional colored objects