Show that linear magnification of an image formed by a curved mirror may be expressed as :
`m=f/(f-u) = (f-v)/f` where the letters have their usual meanings.

Explanation

We know that linear magnification of an image formed by a spherical mirror is given by :
`m=h^(.)/h = -v/u` ………..(i)
However, from mirror formula
`1/v = 1/f - 1/u = (u-f)/(uf)` or `v=(uf)/(u-f)`
`m=-v/u = -1/u (uf)/(u-f) =f/(f-u)`
Again as per mirror formula
`1/u =1/f - 1/v = (v-f)/(fv)`
`therefore = -v/u =-v(v-f)/(fv) = (f-v)/f`.....(iii)