Name: Scattering of Light
Uploaded: 2019-07-19
Duration: 5 min 47 s
Description: When a beam of sunlight enters a dark room through a small hole, its path becomes visible. Wonder why this happens? Let’s find out in this video.

Question

State the cause of dispersion of white light passing through a glass prism. How did Newton show that white light of sun contains seven colours using identical glass prisms? Draw a ray diagram to show the path of light when two identical glass prisms are arranged together in inverted positions with respect to each other and a narrow beam of white light is allowed to fall obliquely on one of the refractive surfaces of the first prism.

Accepted Answer

The splitting of white light into its component colours is called dispersion of light. Light is a combination of different colours. These colours get deviated in a different way when they are passed through a prism. The extent of deviation will be higher for colour with highest wavelength. In other words, the light of different colours travels with the same speed in a vacuum but they travel at different speeds in a refracting medium.

When white light is made to fall on one face of a glass prism, it is observed that it splits into its constituent colours. This was first observed by Sir Newton.

The light emerging from the prism consists of seven colours, namely, violet, indigo, blue, green, yellow, orange and red. The colour band so obtained is called the visible spectrum. It may be noted that of these colours, red is the least deviated; while violet is most deviated.

Consider the following figure. Two identical prisms are placed such a way that the second prism is held in a position along with the first prism but in the opposite direction. The first prism splits the white light into seven colours and the second prism recombines them to form original white light.

Important Questions on The Human Eye and Colourful World

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