Question

Find out the image position formed by the concave mirror, if the first image formed by the plane mirror is taken as an object for the given concave mirror.

• A. $20cm$ from the pole of concave mirror
• B. $30cm$ from the pole of concave mirror
• C. $40cm$ from the pole of concave mirror
• D. $60cm$ from the pole of concave mirror

Answer 1

The correct option is B $30cm$ from the pole of concave mirror

Object distance, $u=-60cm$
Image distance, $v=?$
Focal length, $f=-20cm$

Using mirror formula,
$\frac{1}{v}+\frac{1}{u}=\frac{1}{f}$
$\frac{1}{v}=\frac{1}{f}-\frac{1}{u}=\frac{-1}{20}-\frac{1}{-60}=\frac{-2}{60}$
$v=-30cm$