Question

4.5 cm needle is placed 12 cm away from a convex mirror of focal length 15 cm. Give the location of the image and the magnification.

Answer 1

Object distance, u =12 cm
Image u =?
Focal length, f =15 cm
$\therefore \frac{1}{v}+\frac{1}{u}=\frac{1}{f}\Rightarrow \frac{1}{v}+\frac{1}{-12}=\frac{1}{15}\Rightarrow \frac{1}{v}=\frac{1}{12}+\frac{1}{15}=\frac{9}{60}$
$\therefore v=\frac{20}{3}cm$
$M=-\frac{v}{u}=-\frac{\frac{20}{3}}{12}=\frac{+4}{9}$