Question

Refraction of a light ray at air-glass interface is as shown. If the refractive index of the glass is 1.5, calculate the speed of light of the refracted ray.

• A. $2\times {10}^{8}m/s$
• B. $2.2\times {10}^{8}m/s$
• C. $3\times {10}^{8}m/s$
• D. $6\times {10}^{8}m/s$

Answer 1

The correct option is A $2\times {10}^{8}m/s$

Given:

Refractive index, $n=1.5$
Speed of light in vaccum,$c=3\times {10}^{8}m/s$
Speed of light in medium, $v=?$

We know,

Absolute refractive index (n) is given by,

$n=\frac{c}{v}$

Putting the given values,

$1.5=\frac{3\times {10}^8}{v}$

$v=\frac{3\times {10}^8}{1.5}$

$v=2\times {10}^{8}m/s$