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QuestionPhysicsClass 12

The refractive index of glass is $$1.5$$. From a point $$P$$ inside a glass block, draw rays $$PA, PB$$ and $$PC$$ incident on the glass-air surface at an angle of incidence $$30^o, 42^o$$ and $$60^o$$ respectively.What is the angle of refraction for the ray $$PB$$ ? (Take $$\sin 42^o = \cfrac{2}{3}$$ )
(A) $$0^o$$
(B) $$30^o$$
(C) $$60^o$$
(D) $$90^o$$

According to Snell's Law: $$\cfrac{sin i}{sin r}=\cfrac{n_2}{n_1}$$
Substituting, $$\cfrac{sin 42}{sin r}=\cfrac{1}{1.5}$$
Thus, $$sin r=\cfrac{1.5}{1.5}=1$$
Thus, $$r=90^o$$