Question

A diverging beam of light from a point source S having divergence angle $\alpha$ 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 its refractive index is n, then the divergence angle of the emergent beam is

• A. zero
• B. $\alpha$
• C. $sin^{-1} (1/n)$
• D. $2sin^{-1} (1/n)$

Answer 1

Answer: (B)

$\alpha$

Answer 2

Divergence angle will remain unchanged because in case of a
glass slab every emergent ray is parallel to the incident ray.
However, the rays are displaced slightly towards outer side.
(In the figure OA \\BC and OD || EF)