Ray Optics and Optical Instruments - Result Question 20
20. Light travels through a glass plate of thickness $t$ and refractive index $\mu$. If $c$ is the speed of light in vacuum, the time taken by light to travel this thickness of glass is
[1996]
(a) $\mu t c$
(b) $\frac{t c}{\mu}$
(c) $\frac{t}{\mu c}$
(d) $\frac{\mu t}{c}$
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Answer:
Correct Answer: 20. (d)
Solution:
- (d) Total thickness $=t$; Refrative index $=\mu$ Speed of light in Glass plate $=\frac{c}{\mu}$
Time taken $=\frac{t}{(\frac{c}{\mu})}=\frac{\mu t}{c}$.
where, $t=$ thickness of glass plate
Speed of light in medium
$\nu=\frac{\text{ Speed of light in vaccum }}{\mu \text{ of medium }}$
