The angle of minimum deviation of an equilateral prism is $$30^\circ$$. The velocity of light inside the prism is (velocity of light in vacuum $$= 3 \times 10^8\text{ ms}^{-1}$$)

Solution

For an equilateral prism $$A = 60^\circ$$, so $$\mu = \frac{\sin\left(\frac{A + \delta_m}{2}\right)}{\sin\left(\frac{A}{2}\right)} = \frac{\sin 45^\circ}{\sin 30^\circ} = \sqrt{2}$$. The velocity inside the prism is $$\frac{3 \times 10^8}{\sqrt{2}} \approx 2.121 \times 10^8\text{ ms}^{-1}$$.

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