Question

What is the velocity of light in a medium having refractive index $1.5$?

• A. $3\times {10}^{8}m{s}^{-1}$
• B. $1.5\times {10}^{8}m{s}^{-1}$
• C. $2\times {10}^{8}m{s}^{-1}$
• D. $1\times {10}^{8}m{s}^{-1}$

Answer 1

The correct option is C $2\times {10}^{8}m{s}^{-1}$

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

$\therefore v=\frac{c}{n}$
$v=\frac{3\times {10}^8}{1.5}$
$v=2\times {10}^{8}m{s}^{-1}$

Thus, speed of light in the medium having refractive index $1.5$ is $2\times {10}^{8}m{s}^{-1}$.