In an equilateral prism the ray undergoes minimum deviation when it is incident at an angle of $50^{\circ}$.…

In an equilateral prism the ray undergoes minimum deviation when it is incident at an angle of $50^{\circ}$. The angle of minimum deviation is
  1. $50^{\circ}$
  2. $40^{\circ}$
  3. $25^{\circ}$
  4. $20^{\circ}$

Solution

When a ray undergoes minimum deviation, $i=\frac{A+\delta_m}{2}$
For an equilateral triangle, $\begin{aligned} & A=60^{\circ} \\ \therefore \quad & 50=\frac{60+\delta_m}{2} \\ \therefore \quad & \delta_m=40^{\circ} \end{aligned}$ .

Asked in: MHT CET 2024 (04 May Shift 1)

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