A man uses a concave mirror for shaving. He keeps his face at a distance of `20cm` form the mirror and gets an image which is `1.5` times entarged. Find the focal length of the mirror.

Answer

`60cm`

Explanation

`m = -(v)/(u) = 1.5, v = -1.5u`
`v = -1.5xx(-20)m = 30cm`
`(1)/(f) = (1)/(30) + (1)/(-20) = (2-3)/(60), f = -60cm`.