Kids, why does the light from the sun make rainbows some of the time but not all of the time? It is because raindrops in the air can break up the sun's light into the different colors of light that we can see in a rainbow. You may have seen a rainbow on a day when the sun came out while rain was still falling. You may also have seen one at a waterfall where the water splashed up into a mist, or even in the water from a lawn sprinkler on a sunny day. In this activity, you can try making your own rainbow show! All you need is an adult partner, a garden hose, and a sunny day.
Please note: All chemicals and experiments can entail an element of risk, and no experiments should be performed without proper adult supervision.
With your adult partner, turn on a hose and make a fine spray using a nozzle or your thumb. Move so that you are looking at the water with the sun behind you. Spray harder or softer and higher or lower until you see a rainbow. Try changing your position so that the sun hits your water from a different angle. Or try having your partner spray the water while you view from different angles and distances. If you are successful, note the order of the colors.
Light is an electromagnetic wave of energy. Some electromagnetic waves have higher energies than others. The whole range is called the electromagnetic spectrum. Waves in this spectrum include X-rays, microwaves, radio waves, visible light, and others. The waves of visible light, which is what we can see, are in the middle of this spectrum. Their energies are lower than those of X-rays, but higher than those of microwaves and radio waves. The colors appear in order according to their energy. From the lowest energy to the highest energy the colors appear as
red, orange, yellow, green, blue, indigo, and violet.
Remember it as Roy G. Biv. The waves just beyond red and out of sight are called infrared, while the waves just beyond violet and also out of sight are called ultraviolet. Now that you are done with your lesson, I'm sure that you can think of another way to really enjoy that garden spray in our hot Chicago summer!
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Kathleen Carrado Gregar, PhD, Argonne National Labs
[email protected]
August-September 1995
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Reference: WonderScience 1995, vol. 9, number 4.
