Question

convex len has _ focal lenth ,concave lens has_ focal lenth​

Answer 1

Answer:

this depends on the radius of curvature bro, the focal length is generally the half of radius of curvature

Explanation:

The radius of curvature is the length from the pole of the spherical mirror to the center of the sphere from which the mirror is cut.

you need to know about the parts of a spherical mirror like pole, focus, centre of curvature, principle axis etc.