Question

give the explanation how rainbow is formed??

Answer 1

Rainbow is formed by the process of Diffusion.
Diffusion means that when a narrow white beam of light pass through a refracting medium such as a water droplet from a specific angle it diffuses into its 7 colours.
The band of colours is known as spectrum

Answer 2

Water droplet acts as a prism. When a light or sunlight passes through the rain drop or water droplet then it undergoes refraction then dispersion. After dispersion it undergoes to Total internal reflection. And again refraction. Then it comes out of the water droplet or rain drop as a dispersion means came out as splitting into seven colours i.e. 

Violet, Indigo, Blue, Green, Yellow, Orange and Red. (VIBGYOR)

These colors reach the eyes of the observer and he/she can easily saw the rainbow...

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The phenomenon involved in it are :-

1) Refraction

2) Total internal reflection

3) Dispersion

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Condition necessary to see rainbow are :-

1) Recent rain.

2) Sun must be behind the observer.

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