Question

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

A. separate the red colour apart from the green and blue colours
B. separate the blue colour apart from the red and green colours
C. separate all the three colours from one another
D. not separate the three colours at all

Answer 1

Correct Answer - A
Refractive index of light rays that can just pass through the prism at grazing emergence at 2nd surface is
`mu=(1)/(sin 45^(@))=1.414`
Light havinig refractive index `lt 1.414` takes refraction but light having `mugt1.414` suffers TIR.
`:.` Only red colour light will come out of prism.