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   Secondary Rainbow  

  Primary & secondary bows.  The secondary at right is nearly always fainter than the primary. Its colours are reversed and more widely separated.  These bows were captured by Matt Spinetta in South Dakota on 4th July, 2003.  ©2003 Matt Spinetta.
   
Light can be reflected more than once inside a raindrop. Rays escaping after two reflections make a secondary bow.

The secondary has a radius of 51º and lies some 9º outside the primary bow. It is broader, 1.8X the width of the primary, and its colours are reversed so that the reds of the two bows always face one another. The secondary has 43% of the total brightness of the primary but its surface brightness is lower than that because its light is spread over its greater angular extent. The primary and secondary are are concentric, sharing the antisolar point for a center.