Find the minimum angle of deviation for a prism with angle A = 60° and $μ$ = 1.5.

37° 40° 55° 65°

37°

Minimum Deviation The angle of minimum deviation occurs when i = e and $r_1 = r_2$ and is given by: $μ = \frac{\sin (\frac{A + D_m}{2})}{\sin\frac{A}{2}}$ $⇒ D_m= 2\sin^{−1} (μ\sin \frac{A}{2}) − A$ Substituting $μ  = 1.5$ and A = 60°, $D_m = 2\sin^{−1}(0.75) − 60° = 37°$