Question

The refractive indices of glass and water with respect to air are $\frac{3}{2}$ and $\frac{4}{3}$ respectively. If the speed of light in glass is $2\times 108m/s$. Find the speed of light in water.

Answer 1

$\begin{array}{c}{n}_g=\frac{3}{2}\\ n_w=\frac{4}{3}\end{array}\}\Rightarrow n_g,w=\frac{n_g}{g_w}=\frac{\frac{3}{2}}{\frac{4}{3}}=\frac{9}{8}$
$\therefore \frac{v_w}{v_g}=\frac{9}{8}\Rightarrow V_w=\frac{9}{8}{V}_g=\frac{9}{8}\times 2\times {10}^8$
$=2.25\times {10}^{8}m/s$