Adjust the prism so that the spectrum lands on the paper in the shaded portion of the box. You may have to experiment to find the right height for the prism, depending on the angle of the sun.

Record the ambient air temperature. Then place the thermometers side by side under the spectrum and record the color and temperature readings after a minute or two. (You’ll also learn something about how fast the sun moves across our sky!) It’s best to get at least three sets of temperature readings to ensure accuracy.

Next, move the thermometers such that one is just beyond the red end of the spectrum; record its temperature. Much to his amazement, Herschel found that this area where there was no visible light was the hottest part of the spectrum. He was the first to realize that there is light that we cannot see. The invisible light that he discovered was later named infrared (which means “below the red”) light.

Television remotes use infrared light to communicate with TVs. Herschel and others found that infrared light has all the other properties of light except that we cannot detect it with our eyes. You can prove this by using a mirror to bounce a remote signal toward your television.


Through these experiments, you’ve begun gaining knowledge about the fascinating topics of light and color. Don’t stop here. There are numerous resources in the library and on the web, and there are a number of hands-on science kits that can further illuminate your knowledge of light and color.

Published on May 5, 2009

The son of a son of an engineer, David M. Jones has long been fascinated by science and technology. With two engineering degrees and more than twenty-six years of experience, he recently co-founded Edamar, Inc. and has turned his energies toward helping others learn the fundamentals of science using KitBooks. Learn about Edamar’s exciting new approach to hands-on science at

Copyright 2008. This article originally appeared in The Old Schoolhouse Magazine, Winter 2008/09
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