Question

 What is meant by (i) principal focus of a convex mirror, and (ii) focal length of a convex mirror? 

Answer 1

Definitions-
 (i) Principal focus (F) of a convex mirror - Focus is the point at which the incident rays, parallel to the principal axis, appear to have come from, after reflection.
(i)Focal length (f) - Focal length of a convex mirror may be defined as the distance between its pole and focus.