WHAT IS A RAINBOW?

Author Donald Ahrens in his text Meteorology Today describes a rainbow as 'one of the most spectacular light shows observed on earth'
Indeed the traditional rainbow is sunlight spread out into its spectrum of colors and diverted to the eye of the observer by water droplets
The 'bow' part of the word describes the fact that the rainbow is a group of nearly circular arcs of color all having a common center

 
The rainbow of colors in the order red, orange, yellow, green, blue and violet produced by refraction white light into its component colors.

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Rainbows through the sky.
Notice that the sky inside the rainbow is always
brighter than outside the rainbow.

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As sunlight passes through a drop of water, it is first bend and then reflected
from the back surface of the drop toward the viewer's eye.


When the sunlight enters a raindrop it is refracted or bend and then reflected
from the drop in such a way that the light appears as a spectrum of colors.

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The colors can only been seen when the angle of reflection between the sun,
the drop of water and the observer's line of vision is between 40^° and 42^°.


The amount of bending, known as refraction, differs for light of different colors.
Red light bends the least and violet light bends the most.
The bow is seen usually in the sky opposite the sun at the end of a shower and also in the spray of waterfalls.


The rainbow as an arch of light exhibiting a spectrum of colors in their order caused by drops of water falling through the air.
In the brightest or primary bow, often the only one seen, the colors are arranged with the red on the outside.


Above a perfect primary rainbow is a secondary bow, in which the colors are arranged in reverse order.
This bow is dimmer, because of the double reflection within the drops of water.