Question

In the given figure, a light ray comes out from a medium of refractive index $n=\frac{3}{2}$ to air. Which of the following statement is true ?

• A. Speed of light in the medium is $3\times {10}^{8}m/s$
• B. The refracted ray will bend toward the normal
• C. The refracted ray will bend away from the normal
• D. Speed of light in the medium is greater than the speed of light in air.

Answer 1

The correct option is C The refracted ray will bend away from the normal

We know when light enters from a rarer medium to denser medium it bends toward the normal and when it enters from a denser medium to rarer medium it bends away from the normal.

Generally the refractive index of air is taken as 1 which means that it a rarer medium compared to given medium. So when it comes out from the medium to air it will bend away from the normal.

Also,
Refractive index is defined as speed of light in vaccum to that in medium. A more opticcally dense medium means less speed of light in that medium, clearly the medium is optically dense than air so speed of light in it will be smaller than the speed of light in air.
Refractive index of medium w.r.t air
$\Rightarrow n_{ga}=\frac{speedoflightinair}{speedoflightinthemedium}$
$\Rightarrow \frac{3}{2}=\frac{speedoflightinair}{speedoflightinthemedium}$

Which gives speeed of light in the medium (v) as $2\times {10}^{8}m/s$.