Tuesday, April 12, 2011

Double Rainbows

When u see a double RAINBOW, what do you call the dark portion between the primary and secondary bows...?

any guess...??

Image by Shelby Hogan.

The dark sky between the primary and secondary rainbows is called Alexanders Dark Band.


 In a double rainbow, a second arc may be seen above and outside the primary arc, and has the order of its colours reversed (red faces inward toward the other rainbow, in both rainbows). This second rainbow is caused by light reflecting twice inside water droplets. The region between a double rainbow is dark. The reason for this dark band is that, while light below the primary rainbow comes from droplet reflection, and light above the upper (secondary) rainbow also comes from droplet reflection, there is no mechanism for the region between a double rainbow to show any light reflected from water drops, at all.

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