Question

define the principal focus of a convex mirror

Answer 1

A number of rays parallel to principal axis when reflected appear to meet at a point on principal axis  the point is known as principal  focus of convex mirror.

Answer 2

Explanation:

The principal focus of a convex mirror or of a concave mirror is denoted by F in the optical ray diagram. The principal focus is a point which is found on the "principal axis" of the ray of light travelling through. The point at which the ray or beam of light which are travelling "parallel to the principal axis" either actually in real meets or appears virtually to meet, after the reflection, is called the principal focus.

Principal focus of convex mirror is the point where the ray of light after reflection appears to meet.