Everyone has seen a rainbow, and just about everyone loves getting to see the various colors arching through the sky. When the rainbow is especially vivid, viewers will be able to enjoy all the colors of the visible spectrum.

For those who don’t remember learning this in school, those colors in the rainbow are red, orange, yellow, green, blue, indigo, violet. And they occur in that order from the top down.

This is because when light passes through some type of medium, such as water in this case, it slows down and changes direction. This is a process called refraction.

Sunlight is made up of multiple different wavelengths of light, each of which is affected slightly differently as it passes through the water droplets in the atmosphere. The UK Met Office explains how this works in a rainbow:

“An observer standing in the right place will see the dispersed sunlight reflected back towards them. Light scattered by many drops reaching the observer’s eye will appear as a colourful rainbow. Different colours exit the droplets at angles varying by around two degrees from red to violet. The red light seen by an observer comes from drops slightly higher in the atmosphere than the drops that scatter violet light towards the observer.”

While this is how the refraction works for all types of rainbows, what ends up being visible to a human observer can change depending on a number of factors. For example, when the sunlight is coming through at certain angles or when the moisture in the atmosphere is at different levels, the rainbow may be less vivid or even appear to be missing certain colors.

When the sunlight hits our atmosphere at an angle where it is thicker, such as during a sunrise or sunset, a greater amount of the light in the blue spectrum is scattered out. This filtering of the light means that only those colors that are in the red spectrum remain.

The end result is a rainbow that is primarily, or even exclusively, some shade of red. These are generally called red rainbows or monochrome rainbows. While they do not have the classic look to them, many people think that they are just as beautiful, if not more so thanks to the rareness.

So, if you are lucky enough to be in an area where one forms, now you know how it happened and can better appreciate its beauty.

If you thought that was interesting, you might like to read about the mysterious “pyramids” discovered in Antarctica. What are they?