For a refractive index () = \(\frac{\sin\frac{1}{2} (A + D)}{\sin\frac{1}{2}A}\) D = angle of minimum deviation A = refractive angle of the prism 1.5 = \(\frac{\sin\frac{1}{2} (60 + D)}{\sin\frac{1}{2} \times 60}\) 1.5 = \(\frac{\sin\frac{1}{2} (60 + D)}{\sin 30}\) Sin \(\frac{1}{2}\) (60 + D) = 1.5 * Sin 30 Sin \(\frac{1}{2}\) (60 + D) = 0.75 \(\frac{1}{2}\) (60 + D) = Sin-1 (0.75) but Sin-1 (0.75) = 49o \(\frac{1}{2}\) (60 + D) = 49 60 + D = 2 * 49 = 98o D = 98o - 60o D = 38o