For a rainbow to form, water droplets must be present in the air in front of an observer and the sun must be shining from behind the observer. Rainbows result from the refraction and reflection of sunlight by these water droplets. As sunlight enters a droplet, it is refracted (it slows and bends), with violet light bending the most and red light the least. Much of the light passes on through the drop, but some strikes the backside of the drop at such an angle that it is reflected back and is again refracted as it leaves the drop and passes to the observer's eyes. Because each light ray bends differently from the rest, each ray emerges at a slightly different angle. The colors are thus separated from each other as they emerge, dispersed into a spectrum of colors from violet to red. It takes myriads of droplets (each refracting and reflecting light back to our eyes at slightly different angles) to produce the brilliant colors of a rainbow.
