LOOKING FOR RAINBOWS
by Robert Krampf

This time we are going to learn how to look for rainbows. For many people, seeing a rainbow is a matter of chance, but if you know the science behind it, you will know when and where to look for them. To see that, we will make a rainbow of our own

For this experiment, you will need:

• a sunny day
• a garden hose

Be sure that it is a bright, sunny day, if you want to see a rainbow. You want the sun to be low in the sky, so it is best to do this in the morning or evening, not at noon. Turn on the garden hose. If you have a spray attachment, set it for the finest spray. If you don’t have a spray attachment, put your thumb over the end of the hose to make a spray. Look at the water drops. Do you see a rainbow? Probably not. Notice where the sun is. Watch the water drops as you turn slowly towards the sun. Once you are facing the sun, look carefully at the water drops. See a rainbow? No. Not yet. OK, now keep turning. As you slowly turn, continue to watch the spray. Ahh, there’s the rainbow. Once you see it, notice where the sun is. It is behind you!

In order for you to see a rainbow, the sunlight must enter the raindrop, pass through it, and hit the far side. It then reflects back through the water drop to your eye. In passing through the drop, the light is broken up into colors, just as if it had passed through a prism.

The best time to see a rainbow is when the sun is low in the sky and it is raining in the opposite direction. If it is morning, then the rain should be to the west of you, as the sun is rising in the east. In the evening, the rain should be to the east of you. Once you know where and when to look for them, rainbows are easy to see, but that does not make them any less beautiful.

Reprinted with permission. © 2008. Robert Krampf’s Science Education