Question

A $1cm$ object is placed perpendicular to the principal axis of a convex mirror of focal length $7.5cm$ . Find its distance from the mirror if the image formed is $0.6cm$ in size.

Answer 1

The magnification is given as,

$m=-\frac{v}{u}$

$0.6=-\frac{v}{u}$

The mirror formula is given as,

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

$\frac{1}{0.6u}-\frac{1}{u}=\frac{1}{f}$

$u=5cm$

Thus, the distance from the mirror is $5cm$.