Question

A glass slab of thickness t and refractive index $\mu$. Calculate the time taken by light to travel this thickness.

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

Answer 1

The correct option is D $\frac{\mu t}{c}$

Speed of light in vacuum=$c$

Refractive index $\mu$ is ratio of speed of light in vacuum to the speed of light in the given medium.

Thus $\mu =\frac{c}{v}$

Thus speed of light in the glass slab$=v=\frac{c}{\mu }$

Time taken by light to travel through thickness $t=\frac{t}{v}=\frac{t}{c/\mu }=\frac{\mu t}{c}$