Question

If the velocity of light in vacuum is $3\times {10}^{8}m{s}^{-1}$, the time taken (in nanosecond) to travel through a glass plate of thickness $10cm$ and refractive index $1.5$ is :

• A. $0.5$
• B. $1.0$
• C. $2.0$
• D. $3.0$

Answer 1

The correct option is A $0.5$

Given: $v=3\times {10}^{8}m{s}^{-1},d=10cm$ and $\mu =1.5$

$t=\frac{d}{c/\mu }$

$t=\frac{10\times {10}^{-2}}{2\times {10}^8}$..........$(\because \frac{c}{\mu }=\frac{3\times {10}^8}{1.5}=2\times {10}^8)$

$t=0.5\times {10}^{-9}s=0.5$ nanosecond