Converging rays are incident ono a convex spherical mirror so that their extensions intersect 30cm behind the mirror on the optical axis. The reflected rays form a diverging beam so that their extensions intersect the optical axis 1.2 m from the mirror. Determine the focal length of the mirror.

Explanation

In the case `u = +30`
`rArr v = +120`
`:. (1)/(f) = (1)/(v) + (1)/(u) = (1)/(120) + (1)/(30)`
`f = 24cm`