Question

Light travels through a glass plate of thickness $t$ and refractive index $p$. If $c$ is the speed of light in vacuum, the time taken by light to travel this thickness of glass is

• A. $\mu tc$
• B. $\frac{tc}{\mu }$
• C. $\frac{t}{\mu c}$
• D. $\frac{\mu t}{c}$

Answer 1

Answer: (D)

Total thickness $=t$; Refrative index $=\mu$.
Speed of light in Glass plate $=\frac{c}{\mu }$
$\left[\because v=\frac{\text{ Speed of light in vacuum }}{\text{ R.I. of Medium }}\right]$
Time taken $=\frac{t}{\frac{c}{\mu }}=\frac{\mu t}{c}$
(where $t=$ thickness of glass plate)