Question

A ray of light incidents on a plane mirror at an angle ${30}^{\circ }$, calculate the angular deviation of the reflected ray.

• A. ${60}^{\circ }$
• B. ${75}^{\circ }$
• C. ${120}^{\circ }$
• D. ${90}^{\circ }$

Answer 1

The correct option is C ${120}^{\circ }$

So, let's get clear about what does the angular deviation of a ray means. It means the angle between the initial and final direction of a ray and it tells us by what angle did the ray got diverted from its initial path. Also, the reason of deviation for the ray here in this context is reflection.
Let's use the ray diagram to find out the angular deviation.

From the diagram, we see that the total deviation is ${120}^{\circ }$