Question

A beam of light consisting of red, green and blue colours is incident on a right-angled prism, as shown. The refractive indices of the material of the prism for the red, green and blue wavelengths are 1.39, 1.44 and 1.47 respectively. The prism will ______.

विकल्प

• separate the part of the red colour from the green and blue colours.

• separate the part of the blue colour from the red and green colours.

• separate all the three colours from one another.

• not separate even partially any colour from the other two colours.

Answer 1

The prism will separate the part of the red colour from the green and blue colours.

Explanation:

The critical angles `(C = sin^-1  1/n)` for red (n = 1.39), green (n = 1.44) and blue (n = 1.47) light are 46°, 44°, and 43°, respectively. All coloured rays will strike the hypotenuse face at 45°. Hence, green and blue rays will be totally reflected, while red rays will get through.