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) = 49^o


\(\frac{1}{2}\) (60 + D) = 49


60 + D = 2 * 49 = 98^o


D = 98^o - 60^o


D = 38^o