Question

A beam of light consisting of red, green and blue is incident on a right angled prism. The refractive index 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 part of the red color from the green and blue colors.
• B. separate part of the blue color from the red and green colors.
• C. Separate all the three colors from the other two colors.
• D. not separate even partially any color from the other two colors.

Answer 1

The correct option is A separate part of the red color from the green and blue colors.

At point A, for total internal reflection to take place, $\mu sini>1$

Hence $\mu >\sqrt{2}$ for total internal reflection to take place,

Thus green and blue colours suffer total internal reflection whereas red just refracts and gets separated from the other two.