What causes a secondary rainbow?

A rainbow, with just a hint of a double rainbow above it, arches across a Madison field after a storm moves away. The view is looking east toward Downtown from a hill near Mineral Point Road and Highway M. (Photo credit: State Journal archives). The classic rainbow is a single, bright, colored arc. read more

The secondary rainbow light path involves refraction and two reflection inside the water droplet. The higher order rainbows also formed in the nature but barely seen due to their low visibility. Hope this helps. read more

Secondary Rainbow The secondary rainbow is about 10° further out from the antisolar point than the primary bow, is about twice as wide, and has its colors reversed. According to Schaaf, the light of the secondary bow is one-tenth the intensity of that of the primary bow, given the same viewing conditions. read more

Rays escaping after two reflections make a secondary bow. The secondary has a radius of 51º and lies some 9º outside the primary bow. It is broader, 1.8X the width of the primary, and its colours are reversed so that the reds of the two bows always face one another. read more