# A Certain Material Has Refractive Indices 1.56, 1.60 and 1.68 Rfor Red, Yellow and Violet Lightespectively. (A) Calculate the Dispersive Power. - Physics

Sum

A certain material has refractive indices 1.56, 1.60 and 1.68  rfor red, yellow and violet lightespectively. (a) Calculate the dispersive power. (b) Find the angular dispersion produced by a thin prism of angle 6° made of this material.

#### Solution

Given:-

Refractive index for red light, μr = 1.56

Refractive index for yellow light, μy = 1.60

Refractive index for violet light, μv = 1.68

Angle of prism, A = 6°

(a)  Dispersive power $\left( \omega \right)$ is given by

$\omega = \frac{\mu_v - u_r}{\mu_y - 1}$

On substituting the values in the above formula, we get

$\omega = \frac{\left( 1 . 68 - 1 . 56 \right)}{\left( 1 . 60 - 1 \right)}$

$= \frac{0 . 12}{0 . 60} = 0 . 2$

(b) Angular dispersion = (μv − μr)A
=(0.12) × 6° = 0.72°

Thus, the angular dispersion produced by the thin prism is 0.72°.

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#### APPEARS IN

HC Verma Class 11, 12 Concepts of Physics 1
Chapter 20 Dispersion and Spectra
Q 2 | Page 442