A rainbow is most often viewed as a circular arc in the sky. A rainbow is an excellent demonstration of the dispersion of light.
The water represents a medium with a different optical density than the surrounding air. Light waves refract when they cross over the boundary from one medium to another.
Why is a rainbow a bow—or arc?
A full rainbow is actually a complete circle, but from the ground we see only part of it. From an airplane, in the right conditions, one can see an entire circular rainbow.
Why different colors in rainbow?
Sunlight is made up of many wavelengths—or colors—of light. Some of those wavelengths get bent more than others when the light enters the water droplet.
The angle for each color of a rainbow is different, because the colors slow down at different speeds when they enter the raindrop. The colors of the rainbow are always the same – starting from the outside: red, orange, yellow, green, blue, indigo, violet.
Why red and violet colors on the edges?
The angle of deviation between the incoming light rays from the sun and the refracted rays directed to the observer’s eyes is approximately 42 degrees for the red light. Because of the tendency of shorter wavelength blue light to refract more than red light, its angle of deviation from the original sun rays is approximately 40 degrees. Other colors orange, yellow, green, blue, indigo fall in between.
What makes a double rainbow?
It occurs when refracted light does not escape the raindrop after being reflected the first time. Instead, the refracted light reflects off the raindrop’s surface a second time as well, and this “re-reflected” light exits the drop at a different angle (50° instead of 42° for the red primary bow). This is why the secondary rainbow appears above the primary rainbow with its colors reversed compared to the primary rainbow.
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Rainbow – इंद्रधनुष – Qaus e Qaza