A laboratory experiment from the
Little Shop of Physics at
Colorado State University
Reach for the sky.
Light is a form of electromagnetic radiation.
The rainbow of colors from red to violet is the
spread of different wavelengths that makes up
Of course, there is more to the story...
All forms of electromagnetic radiation (radio
waves, microwaves, infrared, visible light, ultra-
violet, x rays) are really the same basic physical
phenomenon: They are waves of electric and
But they behave very differently. There are two
big differences between different parts of the
spectrum: Wavelength and energy.
The red end of the rainbow corresponds to long wavelength and low energy; the violet end of the spec-
trum, short wavelength and high energy. And the electromagnetic spectrum beyond the rainbow is even
Beyond the violet is the range of very high
energy. The photons of ultraviolet light are
so energetic that they can damage cells. X
rays are even worse, of course; that’s why
you need to limit exposure.
Beyond the red is a much mellower place.
The photons of infrared are so wimpy that
they can only warm you up. Radio waves
are so weak that they can actually go right
In these experiments, we’ll get a chance to
“see” the electromagnetic waves that exist
beyond the rainbow...
Doing the Experiment
This is an open-ended exploration that can
• Rainbow glasses
• IR goggles
• Ceramic heat lamp
• Ultraviolet light (blacklight)
• Thermal imaging camera (optional)
This is an open-ended exploration that can be
done in many different ways which would use dif-
ferent equipment. The thermal imaging camera, in
particular, is hard to find. If you can find one, it’s
great, but if you can’t, you can make the same
point by feeling emitted thermal radiation.
Here is a photo of trees, water and sky through the infrared goggles.
Note the odd patterns of what is dark and