I always love seeing a rainbow after a thunderstorm. But how exactly are we seeing these vibrant colors in the sky?

Let’s go back to science class and talk about refraction and reflection. 

Refraction is the bending of light within a medium, or as light passes from one medium to another. 

Reflection, on the other hand, is when radiation arriving at a surface bounces back, without being absorbed or transmitted. 

Have you ever wondered why you only see a rainbow directly opposite of the sun? Well, this makes sense!

As sunlight moves through a raindrop, it undergoes some refraction. The majority of that sunlight exits the opposite side of that raindrop.

However, some of that sunlight is reflected back to the initial surface of the raindrop, moves through the raindrop again, and is refracted a second time. 

Wow, that’s a lot of science going on there.

So why exactly do we see the same colors in the same arrangement every time?

It’s time to talk about wavelengths. 

The shortest wavelengths of visible light are violet and blue, whereas the longest wavelengths are orange and red. 

Remember the term ROY G BIV (red, orange, yellow, green, blue, indigo, violet)? That will help you remember visible light’s wavelengths in order from longest to shortest.

Longer wavelengths are being refracted less than shorter wavelengths in this instance. Since each wavelength refracts differently, that’s why we see that uniform separation between colors.

As for the arrangement of colors, the color red (shorter wavelength), would angle off the droplet in a way where it would appear to the observer to be on top. On the other hand, the color purple (longer wavelength) would angle off the droplet in a way where it would appear on the bottom to the observer.

Isn’t it fascinating how optical effects can happen in the sky? Now if only Dorothy from The Wizard of Oz could create a scientific version of "Over the Rainbow"...