How Are Rainbows Formed?

Ernie the Eagle

Here are some answers to your kids' questions about Rainbows.

We all love rainbows – but what are they? How are they formed?

In ancient times, people thought the bright bands of color that appeared in the sky were the work of gods or other unseen, mysterious forces. Children were told that they were the result of sprinkled fairy dust. And Irish legend has it that you can find a leprechaun’s pot of gold at the end of every rainbow.

Actually, rainbows appear just after rainstorms or at other times when there is a heavy amount of water in the air. This water is in the form of tiny droplets – mist – that catch the light and deflect (refract) it in the way that a prism does. When the light is deflected (refracted), it is broken up into its basic colors – red, orange, yellow, green, indigo, blue and violet. Hence, we see bands of color in the sky.

Take these same colors and blend them again, and they look white – the color of sunlight!

Usually, we only see one rainbow at a time in the sky, because the light is reflected only once. But sometimes the light bounces inside the droplets of water and is reflected twice. When that happens, two rainbows will appear in the sky: the primary rainbow, and, above it, the secondary rainbow.

Other interesting facts about rainbows:

• A rainbow is actually part of a complete circle. It isn't really an arc. What we see is only half of the entire thing. You can see an entire rainbow by making a mist with your garden hose or by flying over a rainbow in an airplane.

• The light that enters drops of moisture does so in the order of red, orange, yellow, green, indigo, blue and violet. But when the light is refracted, it is sent out (and we see it) in exactly the opposite order: violet, indigo, blue, green, yellow, orange and red.

• Sir Isaac Newton discovered the colors of the rainbow.

• You can always remember the colors if you remember the name Roy G. Biv (red, orange, yellow, green, indigo, blue and violet).

• To see a rainbow, you have to stand with your back to the sun. Rainbows are best seen in the early morning.

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