Given AQ = AR and ∠A = 60° ∴ ∠AQR = ∠ARQ = 60° ∴ r1 = r2 = 30° Applying Snell’s law on face AB sini1 = µsinr1 ⇒ sin i1 = √3 sin 30° = √3 ×
1
2
=
√3
2
∴ i1 = 60° Similarly, i2 = 60° In a prism, deviation δ = i1+i2 - A = 60° + 60° - 60° = 60°