# A Thin Prism is Made of a Material Having Refractive Indices 1.61 and 1.65 for Red and Violet Light. the Dispersive Power of the Material is 0.07. - Physics

Sum

A thin prism is made of a material having refractive indices 1.61 and 1.65 for red and violet light. The dispersive power of the material is 0.07. It is found that a beam of yellow light passing through the prism suffers a minimum deviation of 4.0° in favourable conditions. Calculate the angle of the prism.

#### Solution

The refractive indices for red and yellow lights are μr = 1.61 and μy = 1.65, respectively.

Dispersive power, ω = 0.07

Angle of minimum deviation, δy = 4°

Now, using the relation $\omega = \frac{\mu_v - \mu_r}{\mu_y - 1},$ we  get

$\Rightarrow 0 . 07 = \frac{1 . 65 - 1 . 61}{\mu_y - 1}$

$\Rightarrow \mu_y - 1 = \frac{0 . 04}{0 . 07} = \frac{4}{7}$

Let the angle of the prism be A.

Angle of minimum deviation, δ = (μ − 1)A

$\Rightarrow A = \frac{\delta_y}{\mu_y - 1} = \frac{4}{\left( \frac{4}{7} \right)} = 7^\circ$

Thus, the angle of the prism is 7°.

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#### APPEARS IN

HC Verma Class 11, 12 Concepts of Physics 1
Chapter 20 Dispersion and Spectra
Q 5 | Page 442