Question

A ray of light striking a plane mirror at an angle of $35$ degrees with the normal. Find out the angle of reflection with the normal.

Answer 1

Hint: Reflection is the phenomenon in which a ray of light is incident or made to fall on a surface and it gets reflected through the same path. In this problem, laws of reflection will be followed.


Complete step by step answer:
Step I:
In the process of reflection, two rays were involved: incident ray and the reflected ray. The ray of light that is incident on the surface is called incident ray. The ray of light which reflects back after striking through the surface is known as reflected ray.

Step II:
The normal ray is the ray that divides the incident ray and reflected ray in two equal angles. According to the law of reflection, the angle of incidence will always be equal to the angle of reflection.
$\angle i = \angle r$ ---(i)
Step III:
If a ray of light strikes the plane mirror at angle of ${35^ \circ }$, then
$\angle i = {35^ \circ }$
Step IV:
In equation (i) given that, $\angle i = \angle r$
Therefore,
$\angle r = {35^ \circ }$

Therefore the angle of reflection after the ray strikes the plane mirror is ${35^ \circ }$

Note: It is to be noted that reflection and refraction are two different phenomena. But in refraction, also the angle of incident is equal to the angle of refraction. It has been proved by Snell’s Law. According to Snell’s law, the path of light depends on the refractive index of the two mediums taken. But refraction of light is a phenomenon when the ray of light strikes off and tries to travel through two different mediums like air and vacuum.