A Guide to the Scientific Knowledge of Things Familiar

by Ebenezer Cobham Brewer

In the other rainbow, we see the rays of the sun entering the rain-drops at the bottom, and reflected to the top, whence they reach the eye.

Here the ray SA strikes the drop at A,—is refracted or bent to B,—is then reflected to C, where it is refracted again, and reaches the eye of the spectator.

Here the ray SB strikes the drop at B,—is refracted to A,—is then reflected to C,—is again reflected to D, when it is again refracted or bent till it reaches the eye of the spectator.

Q. Why are the colours of the second bow all reversed?

A. Because in one bow we see the rays which enter at the top of the raindrops, refracted from the bottom:

But in the other bow we see the rays which enter at the bottom of the raindrops (after two reflections), refracted from the top.