Question

Drawing a necessary ray diagram, prove with the help of prism that white light of the sun is a mixture of different colours.

Answer 1

Hint : At first, understand the concept of refraction; check what the factors that affect the angle of refraction are. Check whether the white light from the sun has only one wavelength or has many wavelengths. Use this fact to answer the given question.

Complete Step By Step Answer:
We know that when light travels from one medium to the other, it’s path changes because it’s path changes on entering the other medium.
As a prism is made of glass, the light enters from a material of lower optical density to a medium of higher optical density, thus the speed of light decreases and it bends towards the normal on entering the prism.
While leaving the prism the light enters from a material of higher optical density to a medium of lower optical density, thus the speed of light increases and it bends away from the normal on leaving the prism. When white light or visible light passes through a prism it spreads out as a spectrum of different colour.
Let us draw a diagram

We observe that when light passes through prism it spreads into seven different colours which is also known as VIBGYOR, that is, violet, indigo, blue, green, yellow, orange and red. It is because white light is a mixture of all visible wavelengths. And we know, refraction of ray through a medium depends upon its wavelength, as different colours have different wavelengths so they refract at different angles. The red colour has higher wavelength so it refracts with greater angle while violet has lowest wavelength so it refracts with least angle.
Hence it is proved that the white light of sun is a mixture of different colours

Note :
The light when passes from one medium to another its speed changes, as the wavelength of different colours are different, their speeds are also different when they enter the prism. This is also known as dispersion of light. There are many natural phenomena by which we can observe that white light is a mixture of colour, one of such phenomena is the rainbow formation where we can see the seven colours of light.