how do rain droplets form a stationary rainbow when the rain itself is moving rapidly?

Question

so if light refracts of a raindrop would'nt that just form a small spectrum and refract of other rain drops until weird shaped spectrums are formed?? and why is it always in a arc shape?

Answer 1

When you look at part of a rainbow and see green, it's because that raindrop is in the right position to refract green light from the sun to you. When that raindrop moves, it is no longer in the right position to do so. Another raindrop moving into that spot is now in the right position to do so.

Let's say that raindrop refracts green light 50 degrees. Think of all the places you could put that raindrop so that refracted light from the sun reaches your eye. That would be the shape of the rainbow. If you are on a high building or hill, sometimes you can see a complete circle.

Yes you will get secondary refraction, but the result is random. You see the rainbow because so many droplets are in the same position refracting the same color directly to you.

Answer 2

The rain may be moving but the angle in which the light hits your eyes is not.
Think of it as a big mirror. Place a red dot laser at a single point on the mirror. Mark where the dot reflects to. Now, move the mirror on it's own plane without changeing any angles. You will see that the dot remains in the same place.

Answer 3

If you move RELATIVE TO THE LIGHT SOURCE, the rainbow will move as well.
The speed of the refractive material is not relevant.