Activity 6

What causes Rainbows?


Everyone has seen a rainbow. They are arguably one of the most beautiful displays of nature, and they seem to come in many different sizes, situations, and settings. But what is a rainbow? If you ask, most people will say that a rainbow is "light going through raindrops or something". This is correct, but it's not the complete answer.


  • If you have access to a garden hose, a sprinkler, and a water spout, go outside and try to make your own rainbow!

    • Get a fine misting sprinkler and set the water pressure high enough to get a large volume of water droplets in the air.
    • Based on what we've learned up to now, where should you stand with respect to the water and the sun?
    • Find the shadow of yourself on the ground. Try to measure the angle from the shadow of your head to the rainbow arc. Use the "hand and fist" method to measure this angle: if you stretch out your arm and make a fist, the width of your fist is about ten degrees; the width of a finger at arm's length is about two degrees. Try it!

Go to the second part of the Rainbow Readings to learn more about rainbows and how they are formed.

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Department of Physics and Astronomy, Arizona State University, Tempe, AZ 85287-1504
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