These raindrops are higher than those which cause the "primary rainbow" and are special because they internally reflect the incoming 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 in the image at the top of the page that the sequence of colors in the secondary rainbow is switched compared to the primary bow. Why is this?

Continue to The Blue Sky Activity