Q. The critical angle for refraction from glass to air is 30° and that from water to air is 37°. Find the critical angle for refraction from glass to water
(a)sin-1(5/6)
(b) 51°3′
(c) 61°2′
(d) 63°3′
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Ans: (A)
Sol: Refraction from glass to air , critical angle = 30°
μg sin30° = μa sin90°
Refraction from water to air , critical angle = 37°
μw sin37° = μa sin90°
Let critical angle for Refraction from glass to water = θ
sinθ = sin30°/sin37° = (1/2)/(3/5) =5/6
θ = sin−1(5/6)