Question

An object is placed at 60 cm from the pole of a concave mirror whose focal length is 20 cm.
(ii) Find the magnification produced by the mirror.

Answer 1

Given :
Focal length, $f=-20cm$
Object distance, $u=-60cm$

Using mirror formula,
$\frac{1}{\text{f}}=\frac{1}{\text{v}}+\frac{1}{\text{u}}$
$\frac{1}{\text{-20}}=\frac{1}{\text{v}}+\frac{1}{\text{-60}}$
$v=-30cm$

Magnification:
$m=-\frac{v}{u}$
$m=-\frac{(-30)}{(-60)}$
$m=-\frac{1}{2}$