rainbows/sunbows and dark sky regions?

Question

When there's a solar halo (a "glory" around the sun, or sunbow), I notice that the region between the ring and the sun looks darker than the rest of the sky. Even though it's closest to the sun!

When there's a double rainbow, I notice that the region between the two bows looks darker than the rest of the sky.

Can anyone explain the optics of this? What's going on...

Answer 1

The area between the primary and secondary rainbows is called Alexander's dark band.

Wikipedia is as good a place to start as any
http://en.wikipedia.org/wiki/Alexander's_band