Question

Question 2
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 $3\times {10}^8{\text{m s}}^{-1}$.

Answer 1

Refractive index of a medium, $n_m$ = $\frac{\text{Speed of light in vacuum}}{\text{Speed of light in the medium}}$

Speed of light in vacuum, $c=3\times {10}^8{\text{m s}}^{-1}$

Refractive index of glass, $n_g=1.50$

Speed of light in the glass, $v=\frac{\text{Speed of light in vacuum}}{\text{Refractive index of glass}}$
$v=\frac{c}{n_g}$
$v=\frac{3\times {10}^8}{1.5}=2\times {10}^8{\text{m s}}^{-1}$

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