Question

An object of height $1.2m$ is placed before a concave mirror of focal length $20cm$ so that a real image is formed at a distance of $60cm$ from it. Find the position of an object. What will be the height of the image formed?

Answer 1

Given :-

$h_0=1.2m$

$f=-20cm$

$\nu =-60cm$

from mirror formula,

$\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$

$\frac{1}{-60}+\frac{1}{u}=\frac{1}{-20}$

$\frac{1}{u}=\frac{1}{60}-\frac{1}{20}=\frac{-2}{60}$

$u=-30cm$

Magnification, $m=\frac{-v}{u}=\frac{-\left(-60\right)}{-30}=-2$

$m=\frac{h_i}{h_0}=-2$

$h_i=-2\times 1.2=-2.4m$

$h_i=-2.4m$