This amazing photo was taken by Manolis Shamanos in Samos, a Greek island in the eastern Aegean Sea.

This amazing photo was taken by Manolis Shamanos in Samos, a Greek island in the eastern Aegean Sea.As you can see, there is a double rainbow in the image. But, how does this happen?Firstly, we need to understand how a primary rainbow is formed.This optical effect occurs as sunlight enters a raindrop. The beam of light is slowed down and is refracted, dispersed and reflected. Light essentially travels in waves of energy and appears white due to the combination of colours in that single wave of energy. When light bends, individual colours will separate with violet light refracting the greatest and red light refracting the least. This is the reason blue is found at the inside of the bow and red on the very outside.The critical angle of water is 48°, thus any light that hits the raindrop at an angle greater than this is internally reflected towards our eyes. Each ray of light is dispersed at a different angle, which causes the “bow” appearance.While a primary rainbow is visible when light is reflected once off the back of a raindrop, a secondary rainbow is spotted when light is reflected twice in a more complicated pattern. When a secondary rainbow appears you will notice two things; firstly, the colour order is reversed and secondly the colours are not as sharp as in the primary rainbow.The reversal of the colour order is due to the fact that the ray of light is reflected twice within the raindrop; the second reflection inverts the order of the colours. Also attributed to the number of reflections is the loss of colour intensity, with each reflection causing the bow to appear dimmer.Jean. -- source link

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