Question

Light enters from air to glass having refractive index $1.50$. What is the speed of light in the glass? The speed of light in vacuum is $3\times {10}^{8}m{s}^{-1}$.

Answer 1

Given:
Speed of light in vacuum, $c=3\times {10}^{8}m{s}^{-1}$
Refractive index of glass, $n_g=1.50$

Refractive index of a mediumis given by:
$n=\frac{c}{v}$
where:
$n:\text{Speed of light in vacuum}$
$v:\text{Speed of light in medium}$

$v=\frac{c}{n}$
$v=\frac{3\times {10}^8}{1.50}=2\times {10}^{8}m{s}^{-1}$

Therefore, the speed of light in the glass is $2\times {10}^{8}m{s}^{-1}$.