The refractive index of the material of a prism
is ``\sqrt2`` and the angle of the prism is 30°. One of the
two refracting surfaces of the prism is made a mirror
inwards, by silver coating. A beam of
monochromatic light entering the prism from the
other face will retrace its path (after reflection from
the silvered surface) if its angle of incidence on the
prism is :-
(1) 60°
(2) 45°
(3) 30°
(4) zero