Question

A square wire of side $1cm$ is placed perpendicular to the principal axis of a concave mirror of focal length $15cm$ at a distance of $20cm$. The area enclosed by the image of the wire is

• A. $4c{m}^2$
• B. $6c{m}^2$
• C. $2c{m}^2$
• D. $8c{m}^2$
• E. $9c{m}^2$

Answer 1

Answer: (E)

Given focal length of concave mirror
$f=-15cm$ $u=-20cm$
Magnification $m=\frac{f}{u-f}$
$=\frac{-15}{-20+15}$
$m=3cm$
The area enclosed by the image of the wire
$=m^2$ $=9cm$