How are rainbows formed?

Rainbows are one of the most admired meteorological phenomena across the globe, but how are they formed?

Rainbows are formed when light from the sun is scattered by water droplets (e.g. raindrops or fog) through a process called refraction. Refraction occurs when the light from the sun changes direction when passing through a medium denser than air, such as a raindrop. Once the refracted light enters the raindrop, it is reflected off the back and then refracted again as it exits and travels to our eyes.