Rainbows

Everyone knows what a rainbow is when they see one in the sky. But not everyone realizes that the Sun helps make rainbows.

A rainbow happens because of dispersion; which is the separation of white light into the colors of the spectrum. As sunlight shines through rain, each raindrop acts like a prism and the inside of a concave mirror. This means that the sunlight is not only divided into the different colors of the spectrum but that it is also reflected down to the ground.

When you look up and see a rainbow what you are seeing is different than what anyone else can see. Because the reflection comes back to Earth at different angles no two people will ever see a rainbow in the same way. The dispersed rays of light reach Earth differently. At times rainbows seem to have more or less of the colors that they are made up that than at other times. The colors are always present but how you can see them depends on the reflection down to Earth.

There are two types of rainbows. Primary rainbows are very bright because only one reflection is taking place inside a raindrop. Secondary rainbows are dimmer and are caused by two reflections happening inside a raindrop.

Did you know that the colors of a rainbow aren't always in the same order. You may wonder why this is true. The differences in the index of refraction are the cause for the order of the colors. The outer edge of a primary rainbow will be red and the inner edge will be violet. A secondary rainbow will be just the opposite with the outer edge violet and the inner edge red. So the next time you observe a rainbow you can impress everyone by informing them whether they are looking at a primary or a secondary rainbow.

It is possible to see a rainbow in another shape than the well known arch? If you are ever in a plane and see a rainbow you may actually have the opportunity to see a "round" rainbow.

Rainbows are a beauty of nature and the Sun's interaction with water creates them. This is just another example of how the Sun is man's friend.