Optics 2 Question 13
13. 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) $2 \sin ^{-1}(1 / n)$
$(2000,2 M)$
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Answer:
Correct Answer: 13. (b)
Solution:
- 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 $O A | B C$ and $O D | E F$ )
