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. $\frac{t c}{\mu}$
• 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)