| April Showers Bring Rainbows! |
In The Rainbow Web, the little spider saw a tiny rainbow when the sun shone through a drop of dew. This is because sunlight, or white light, is actually made of many colors. When the sunlight enters the drop of water, it separates into waves, or bands, of colors. The color waves hit the back of the dewdrop and bend back, or change direction. Each wave is reflected back, like your face when you look in a mirror. As the color waves bounce back and come out of the drop, they bend, or change direction, again. It is these color waves that make the rainbow you see.
Why do we see one big rainbow instead of many tiny rainbows in the sky?
A rainbow in the sky is made by millions of raindrops, not just one. As the sun shines through these raindrops, each drop reflects back all of the colors. But you can only see one color from each drop. Remember how the color waves bend as they come out of the raindrop? As the color waves from each drop come towards you, most of them bend away so that you can’t see them from where you are standing. You are able to see only one color from each drop. You see red or orange from raindrops that are highest in the sky and blue or violet from the drops that are lowest. Together, these color waves make the whole rainbow!
Why don’t we see a rainbow when the sun shines into a lake or the ocean?
For one thing, the sunlight can’t shine through them. Some sunlight reflects off the top of the water, but most of it is absorbed. Think how a sponge soaks up, or absorbs, water. The ocean soaks up, or absorbs, the light. As you go deeper under water, there is less and less light. We need light to see colors. Have you ever noticed how colors begin to look gray or black at night? After awhile, all the colors start to look the same. As you go deeper underwater, it also gets harder to see colors.
Do all colors underwater look gray at the same time?
Underwater, the longest color wave is absorbed first. This is the color red. So as you go deeper underwater, red objects get harder and harder to see. At about 40 feet, the color red looks gray. This is one reason why many deep sea fish and animals are colored bright red. It helps them to hide from other hungry animals.
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On what kind of days do you see rainbows? Do you see them on bright, sunny days? Do you see them on gray, cloudy days? You need to have rain to see a rainbow. But you also need to have sunlight.
The best time to see a rainbow is right after it has rained, and the sun is starting to come out. This is why springtime is the time for rainbows. In the winter, the rainstorms can last all day, and the sky is usually covered with dark, gray clouds. In the spring, you have rain showers that last a short time. After the shower is over, the clouds move, and the sun starts to shine through them. There are still raindrops in the sky, though. So, the sun shines through these raindrops, making a rainbow in the sky. |
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This month’s activity is a sample from the Rainbow Web CD-ROM: “Rainbow Math.” As students measure the colors in a rainbow, they are introduced to the concepts of the color spectrum and the difference in color wavelengths. The length of a color wave can determine how fast a color is absorbed.
Teaching Suggestions: Coloring the rainbow is optional, especially if the students are learning to recognize the color words. Have all the yarn precut to the same length, the length of the longest color red. Provide each student with a set of rainbow-colored yarn. Then have the students cut the yarn to the correct length for each color and glue it in place.
Alternative: Use colored adhesive dots to represent raindrops. Fill in each band of the rainbow with colored dots. Then count how many dots were needed for each color and record the results on a pictograph or a bar graph.
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