Let the sun shine on, behind me, then!
The waterfall that splits the cliffs’ broad edge,
I gaze at with a growing pleasure, when
A thousand torrents plunge from ledge to ledge,
And still a thousand more pour down that stair,
Spraying the bright foam skywards from their beds.
And in lone splendour, through the tumult there,
The rainbow’s arch of colour, bending brightly,
Is clearly marked, and then dissolved in air,
Around it the cool showers, falling lightly.
There the efforts of mankind they mirror.
Reflect on it, you’ll understand precisely:
We live our life amongst refracted colour.
-- Johann Wolfgang Von Goethe, Faust
Rainbows can often be seen in the spray from a waterfall or a garden hose. Outside the primary rainbow, a secondary bow is sometimes visible, as it is in this photo. The colors of the secondary bow are fainter and in reverse order because the rays of sunlight are relected twice inside each droplet, versus just once for the primary bow.
Although a rainbow formed in spray seems closer than a conventional rainbow, they are both virtual images effectively formed at infinity. This can be frustrating for a photographer who dosn't have a wide-angle lens, since "backing up to fit it all in" doesn't work -- the bow remains the same angular size no matter how far away from the spray you are!
This waterfall, appropriately named Rainbow Falls, is located in Devils Postpile National Monument, California.
This photograph appeared on NASA/USRA's Earth Science Picture of the Day site on October 6, 2004.