Ray Optics And Optical Instruments Ques 3
3. The angle of a prism is ’ $\mathrm{A}$ ‘. One of its refracting surfaces is silvered. Light rays falling at an angle of incidence $2 \mathrm{A}$ on the first surface returns back through the same path after suffering reflection at the silvered surface. The refractive index $\mu$, of the prism is :
[2014]
(a) $2 \sin \mathrm{A}$
(b) $2 \cos \mathrm{A}$
(c) $\frac{1}{2} \cos \mathrm{A}$
(d) $\tan \mathrm{A}$
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Answer:
Correct Answer: 3.(b)
Solution: (b)
According to Snell’s law $\mu=\frac{\sin \mathrm{i}}{\sin \mathrm{r}}$
$ \Rightarrow(1) \sin 2 \mathrm{A}=(\mu) \sin \mathrm{A} \Rightarrow \mu=2 \cos \mathrm{A} $
BETA
