Submodule 4: Secondary Rainbows
Steve Beeson, Arizona State University
The higher raindrops will internally reflect the sunlight twice rather than just once.
Notice that the sunlight hits the bottom of the raindrop to make the secondary rainbow. There is still sunlight hitting the other parts of the raindrop. However, some of the light is simply transmitted through the raindrop without reflecting, and some light is reflected and refracted, but not into our eyes. That light is for someone else's rainbow.
Notice also that the red and blue lines are switched in comparison with the colors from the raindrops making the primary rainbow.
We find that the secondary, outer rainbow goes from red on the inside to violet on the outside.
Light & Optics
Rainbows 1st Page