Question

Explain the Step-by-Step process that takes place in the formation of Rainbow.

Accepted Answer

The formation of a rainbow is described step by step below:

1. Sun Rays Strikes Raindrop
White light from the sun should hit the water droplets at a certain angle. The angle formed is very crucial since it determines whether the rainbow will be formed or not. Rainbows form mostly at dawn or late afternoon since it is best if the sun is fairly low in the sky and provides the ideal angle to form the rainbow. When the angle is not appropriate, we are not able to see the rainbow.
2. Some sunlight is reflected
When the rays from the sun strike or come into contact with droplets of water, the light from the sun is reflected. In the process, the light obeys the law of reflection. It can be better understood when we see through a glass window, but, at the same time, our reflection can be seen. This is because the window both transmits and reflects light. Water can do this too.

3. Rest of Light Gets Refracted
The light that is not refracted crosses the boundary layer of air and water and slows down since water is denser than air. The reduction of speed makes the path of the light bend, which is called refraction. This is the reason why the rainbow is always curved or bent towards the normal line.
4. White Light Splits into Different Colours
White light is made up of a spectrum of colours, each having its wavelength. Different wavelengths travel at different speeds while they encounter a change in the medium that is denser or less dense; the speeds are affected by the difference in amounts. Hence, the colours separate. This phenomenon is known as Dispersion. This is why the rainbow has got different colours.
5. Lights Get Reflected Behind the Rain Drop
When light hits the water-to-air interface at the rear of the raindrop, it forms an angle. If the angle of incidence is greater compared to the critical angle, Total Internal Reflection occurs, and the rainbow can be seen. Whereas, if the angle is lesser than the critical angle, the rainbow formed will not be visible.

6. More Refraction Takes Place
As the light exits the raindrop, its speed changes. Since at this point, movement of the light is away from a denser (water) to a less dense (air) medium, the speed is thus enhanced. The rise in the speed causes the light waves or path of the light to bend away from the normal line. This is another example of refraction. This refraction contributes to the shaping of the rainbow.
7. Colour Forms With More Dispersion
As the rays get refracted once more, the various wavelengths are affected to different extents and enhance the clear formation of the rainbow colours. With the further separation of the component colours of white light and refraction, the definite colours and shape of the rainbow are visible with dispersion.

Explain the Step-by-Step process that takes place in the formation of Rainbow.

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