A prism of glass is shown in figure A, ray incident normally on one face is totally reflected. If θ is 45°, the index of refraction of glass is _______ .
(A) < √2 (B) > √2 (C) = 2 (D) None of these
The correct option is (B) > √2.
For total internal reflection i > θc ......(1)
when θc is critical angle
sin θc = (1/η) i.e. η = (1 / sin θc)
i = 45°
hence 45° > sin –1(1/η) From (1)
sin 45° > (1/η)
(1 / √2) > (1/η) hence η > √2