As a child, I marveled at double rainbows, and their origin โ the double internal reflection of sunlight in drops of watery mist. They are very cool, and not because of fairies or pots of goldโฆ =)
Raindrops are not shaped like drops โ the coherence of rainbows would not occur with teardrops. With spheres, you get internal reflection bounces sending the light back to the viewer, but slightly refracted, generating the color bands (diagrams). So, the color coherence is due to the angle between the viewer and the array of spheres.
The sun has to be behind you. I have always suspected that if the earthโs horizon was not there or if you could view from a high platform with the sunlight streaming below, you would see a “rain circle” rather than a half-circle “bowโ. It was just a theory, as I never got high enough.
I finally saw a full rain circle a few days ago. It was too big to capture in frame, but here is a quarter of it.
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