Question

A ray of light is incident on different media at an angle of 60° as shown in the figure. In which of the following media the speed of light is slowest?

• A. 1
• B. 2
• C. 3
• D. same in all

Answer 1

The correct option is C

3

When light ray enters a denser medium from a rarer medium, it gets slowed down and bends towards the normal.
Therefore, in such cases, the angle of refraction will be less than the angle of incidence.

Angle of incidence is same for all three media. Angle of refraction for the different media are:

$r_{Medium1}={60}^{\circ }$
$r_{Medium2}={45}^{\circ }$
$r_{Medium3}={30}^{\circ }$

Here, the angle of refraction in medium 3 is the smallest. Therefore, medium 3 is the densest medium among the given three media and the speed of light will be minimum in medium 3.