Just after a rain, when the sun emerges from behind the clouds, check the sky for a rainbow (or two). Actually, it must still be raining somewhere in the sky for a rainbow to form. The sunlight is refracted (bent) and reflected (bounced back) by the raindrops, which act like tiny prisms. The seven colors we see in a rainbow are red, orange, yellow, green, blue, indigo and violet. (Just remember Roy G. Biv to recall the colors in their proper order).
Rainbows figure in many folks mythologies, and they are not generally welcome signs. This is not uncommon for infrequent phenomena. In some cultures the rainbow is seen as a snake. In others, the ground where the rainbow touches is considered unhealthy. You’ve probably heard that there’s a pot of gold at the end of the rainbow. Now that’s more like it!
Create a Rainbow With a Garden Hose
You can make your own rainbows (minus the pot of gold!) with a garden hose. The sun has to be shining (just like it does for the real thing), and you should position yourself with your back to the sun. Spray a fine mist in front of you, preferably against a dark background so that the colors will really stand out. Early morning, or late afternoon, is best for this experiment, because the sun’s rays are slanting lower in the sky. Can you make out all the colors?
Make a Rainbow Indoors
You can even make rainbows indoors, without getting wet! Fill a glass with water (make sure it is full to the top) and set it on a window sill in bright sunlight. It should project over the inside ledge just a bit. Put a white sheet of paper on the floor beneath the windows, and a rainbow will magically appear on the paper.
A prism will do the same thing. You can hang a prism in a sunny window, or make some preparations for an even more vivid display of the spectrum colors. Just as the rainbows you made with the garden hose outdoors showed up best against a dark background, so will your prism bows work better in a darkened room. If you have pull shades in a south-facing room, ask your parents if you can make a tiny pinhole in a color of the shade, just big enough to let in a beam of light. Place your prism in the path of the light, and see how it projects a rainbow on the opposite wall.
[Image: Courtesy of Mike Crowley; available for sale at his website Life in the Northwoods]