What are rainbows made up of?
Rainbows have no physical properties, though an argument could be made for them being made up of light. They are caused by the reflection and refraction of sunlight through water droplets in the atmosphere. The water droplets act as individual refractors and reflectors that “split” (refract) the light into the respective colors of the rainbow. The refracted light is reflected off the back surface of the individual rain drops and to the observer.
