Question

A ray of light is incident on a plane mirror at an angle of ${30}^{\circ }$. What is the angle of reflection?

Answer 1

Step 1: Given that:

The angle made by the incident ray with the plane mirror= ${30}^0$

It can be drawn here,

Step 2: Calculation of angle of reflection:

1. The angle made by the incident ray is called the angle of incidence($\angle i$)​.
2. The angle made by the reflected ray with the normal is called the angle of reflection($\angle r$).
3. According to the laws of reflection, the angle of reflection is equal to the angle of incidence, that is $\angle i=\angle r$ .

In the given diagram,

It is clear that,

The angle made by the normal with the plane mirror= ${90}^0$

That is,

${30}^0+\angle i={90}^0$

$\angle i={90}^0-{30}^0$

$\angle r={60}^0$

As,

$\angle i=\angle r$

$\angle r={60}^0$

Thus,

The angle of reflection will be ${60}^0$ .