question_answer

State the cause of dispersion of white light by a glass prism. How did Newton, using two identical glass prisms show that white light is made of seven colours? Draw a ray diagram to show the path of a narrow beam of white light, through a combination of two identical prisms arranged together in inverted position with respect to each other, when it is allowed to fall obliquely on one of the faces of the first prism of the combination.

Answer:

When a beam of white light enters a prism, it gets refracted at point and splits into its seven constituent colours. This splitting of the light occurs because of different angles of bending for each colour and this different angles of bending occurs because different component of light faces different refractive indices when passing through the glass prism.

Firstly, Newton made white light to fall on a prism, this cause dispersion of white light into seven colours. Newton then placed an inverted prism in the path of a colour band of seven colours. Only a beam of white light comes out from the second prism. So Newton concluded that white light comprises of seven component colours.