Q 12-09-016NEETNEET 2020Top questionMedium
A ray is incident at an angle of incidence $i$ on one surface of a small angle prism (with angle of prism A) and emerges normally from the opposite surface. If the refractive index of the material of the prism is $\mu$, then the angle of incidence is nearly equal to :
Answer: (C) $\mu A$
The ray emerges normally, so the angle of refraction at the second face is $r_2 = 0$. Since $r_1 + r_2 = A$, $r_1 = A$.
At the first face, for small angles, $\sin i \approx i$ and $\sin r_1 \approx r_1$:
$$i = \mu r_1 = \mu A$$
Solution by Sreeraj P, M.Sc Physics