Draw a diagram to show the refraction of light through a glass prism. On this diagram, mark (i) incident ray (ii) emergent ray, and (iii) angle of deviation.(b) What is a rainbow? What are the two conditions necessary for the formation of a rainbow in the sky?(c) What acts as tiny prisms in the formation of a rainbow?(d) Name the process which is involved in the formation of a rainbow.(e) What are the seven colours seen in a rainbow?

(a) It can be shown with the help of the following diagram:

(b) A rainbow is an arch of seven colours (violet, indigo, blue, green, yellow, orange, and red) formed in the sky when the water droplets in the atmosphere cause the dispersion of sunlight. 

The two conditions necessary for the formation of a rainbow in the sky are as follows:

1. The sun should be shining.

2. It should be raining at the same time.

(c) Raindrops act as tiny prisms in the formation of a rainbow.

(d) The process involved in the formation of a rainbow is the 'dispersion of sunlight'.

(e) The seven colours seen in a rainbow are red, orange, yellow, green, blue, indigo, and violet.

Explanation

The phenomenon of splitting white light into its components colours (violet, indigo, blue, green, yellow, orange and red) while passing through a prism is known as the Dispersion of light. In the spectrum, red is seen at the top as it has the longest wavelength whereas violet is seen at the bottom of the spectrum as it has the shortest wavelength.

The cause of the dispersion of light through the prism is because white light is a mixture of seven different colours and they get refracted (bend) at different angles in the prism medium due to differences in their speed and wavelengths. So they get separated.

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Updated on: 10-Oct-2022

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