About Alexander’s band
- Alexander’s band is named after Alexander of Aphrodisias, an ancient Greek philosopher who commented on the effect in his writing.
- The darker area between primary and secondary rainbows can be explained by the fact that fewer photons are directed from that area of the sky toward an observer.
- The raindrops that form a primary rainbow all direct exiting light downwards towards an observer so away from Alexander’s band.
- The raindrops that form a secondary bow all direct light upwards, so away from Alexander’s band, before a second internal reflection directs light downwards towards an observer.
- Plenty of light is scattered into the area between primary and secondary rainbows but very little of it travels towards an observer.