Question

Principal focus of the lens​

Answer 1

Answer:

The principal focus of a convex lens is defined as the point on which the principal axis of the light is parallel to the principal axis that converges after the refraction from the lens. The principal focus of concave lens is when the light rays get diverged and appear to form a single point.

Answer 2

Answer:

The principal focus of a lens is a point on its principal axis wherein the rays of light parallel to it and after passing through it converge (for a convex lens) or appear to diverge (for a concave lens). The principal focus of a lens is denoted by the letter F.