question_answer

A diverging beam of light from a point source S having divergence angle a, falls symmetrically on a glass slab as shown.  The angles of incidence of the two extreme rays are equal.  If the thickness of the glass slab is t and the refractive index n, then the divergence angle of the emergent beam is  [IIT-JEE (Screening) 2000]

A)            Zero

B)            a

C)            \[{{\sin }^{-1}}(1/n)\]

D)            \[2{{\sin }^{-1}}(1/n)\]

Correct Answer: B

Solution :

                   Since rays after passing through the glass slab just suffer lateral displacement hence we have angle between the emergent rays asa.