Question

A motor car is fitted with a rear view mirror of focal length 20 cm . A second motor car 2 m broads and 21.6 m high is 6 m away from first car. Find the position of second car as seen in the mirror of the first car .

Answer 1

Given,

Focal length, $f=20cm$

Object distance, $u=6m=600cm$

Image distance, $v=$?

from mirror formula

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

$\frac{1}{20}=\frac{1}{v}-\frac{1}{600}$

$\Rightarrow$ $\frac{1}{v}=\frac{1}{20}+\frac{1}{600}$

$=\frac{620}{2\times 600}$

$\frac{1}{v}=\frac{31}{600}$

$v=\frac{600}{31}=19.35cm$

Hence, the position of second car as seen in the mirror of first car is $19.35cm$ back of the mirror