Question: what causes a rainbow

Zena Hadjivasiliou answered on 14 Mar 2015:

A rainbow is caused when white light goes through rain droplets, which is why we see rainbows when it gets sunny right after it rained. White light is actually made up of all other colours that turn white when they come together (this is something you learn more about in A level physics and it has to do with the way in which light waves of different colour interact with each other). When there are still some droplets of water in the air and the sun comes out white light goes through the droplets and splits up into all the colours that make it up. This happens because the speed at which the light travels changes when light moves from air to water (the droplet!). This forces white light to bend, and then bounce of the other end of the droplet. All the different colours that make up white light have different properties so they bend and move through the droplet in a different way and come out of the droplet in different ways, which means that end up splitting and so we see all the colours one by one!