|T H E N I H C A T A L Y S T||M A Y J U N E 2005|
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A rainbow is a fantastic sight. Its the momentary convergence of light, water vapor, and angles, and can all be explained by math (which youll encounter soon enough). Actually, the mathematical explanations themselves are beautiful, though not in the way of a rainbow.
Fortunately, you dont need to stare at the sky just waiting for things to fall into place for the perfect rainbowyou can create your own, observe reflection and refraction, and make your own rainbow dance.
For this experiment, you will need:
A sunny day
A white piece of paper taped to a piece of cardboard
A mirror small enough to fit into a shallow dish
A shallow dish
Your favorite set of crayons, colored pencils, or watercolors (not at all optional!)
Fill the shallow dish about three-quarters full of water. Place the mirror in the dish at an angle such that some of the mirror is in the water and some of it is not. (You need the light from the sun to shine through the water and catch the reflection of the submerged mirror.) Take the paper (taped to the cardboard because light would shine right through just a plain piece of paper) and hold it up to the reflection the mirror makes. The reflection of the portion of the mirror not in the water will appear as a bright white spot on your piece of paper, but if you move the paper to see the reflection of the mirror that is inside the water you get your rainbow!
If you are doing this experiment using a window, tape the paper to a sturdy surface and draw what you see. Just a few changes you can make and observe are:
How does the intensity of the rainbows colors change when the angle of the mirror changes?
How does your rainbow look when you step away?
What changes when you add red food coloring to the water? What about blue? Green? (You could, of course, use your watercolors, but depending on the size of your dish, this could use quite a bit of your lovely watercolors. . . stick with the food coloring for quick results.)
Have fun with your rainbow, and if you want to get a teacher on your good side, ask her or him about why the colors are reversed in the second half of a double rainbow. Let me know what happens.
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