If an object of height l is placed perpendicularly on the principal axis of a spherical mirror at a distance u from it, prove that the height of its image, `l' = l((f)/(u-f))`

Explanation

We know,
`(1)/(v)+(1)/(u)=(1)/(f) or, (1)/(v)=(1)/(f)-(1)/(u) = (u-f)/(fu) or, (v)/(u)=(f)/(u-f)`
`therefore "Linear magnification," " " m=(l')/(l)=(v)/(u)=(f)/(u-f)`
[considering mod value of m only]
`or, " " l' = l((f)/(u-f))`