Question

State that the following statement is true or false,
A ray of light parallel to the principal axis, after reflection, will pass through the principal focus.
(A) True.
(B) False.

Answer 1

Hint: The light rays that pass through the straight line can only be reflected by two types of mirror. They are convex mirrors and concave mirrors. The concave mirror is a mirror that is curved inward and the convex mirror is curved outward.

Complete solution:
Convex mirror:
As we know that the convex mirror is outwardly curved in which the light rays that travel in a straight line hit the surface of the mirror, then the reflected light rays diverge from the principal axis. The principal axis is nothing but the straight line that passes through the centre of the spherical mirror, that is it passes through the centre of curvature of the mirror. Since, the parallel light rays that get reflected from the convex mirror get diverged, the reflected light rays do not pass through the principal focus.

Concave mirror:
We know that the concave mirror is an inward curved mirror in which the light rays that travel parallel to the principal axis when hits the reflecting surface of the mirror, the reflected ray gets converged towards the principal axis. The converged rays then pass through the principal focus of the mirror. The point where the incident rays of the light gets focused is called the principal focus.

Therefore, the light ray parallel to the principal axis, after reflection, will pass through the principal focus.

Hence, the option (A) true is the correct answer.

Note: The nature of the image that is formed due to the object varies from one mirror to the other. The nature of the image that is formed due to a convex mirror is virtual and erect, virtual means the image is nearly or more or less as detailed as the object and erect means the image formed is upright or straight. The nature of an image formed in a concave mirror is real and inverted, real means the image that formed is not an imitation or artificial but it looks exactly as that of the image and inverted means the image formed is upside down.