rainbows

[DaveH3]

I can explain how rainbows work, why they form, height above horizon etc, but can anyone tell me why the overall picture or contrast is always brighter on the inside of the arc than the outside?

[mibn2cweus]

Most of the light which enters and is reflected by a raindrop does not contribute to the rainbow. Raindrops below the primary rainbow reflect this �extra� sunlight at random angles which are not partitioned into colour bands but only brighten the sky. Light which strikes a raindrop at an angle to sharp to form the colours of the rainbow are mostly scattered outward away from the observer.

To see the angles of refection within a raindrop see
Light Sky Under Rainbow

To appreciate the degree of contrast see also Alexander�s Dark Band

[DaveH3]

Thanks for that mibn2cweus, I understand now.