Question

When an object of height 1 cm is kept at a distance of 4 cm from a concave mirror, its upright image of height 1.5 cm is formed at a distance of 6 cm behind the mirror. Calculate the focal length of the mirror.

Answer 1

u = - 4 cm

v = 6 cm

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

$\frac{1}{f}$ = $\frac{1}{-4}$ + $\frac{1}{6}$

f = -12 cm

Focal length of the mirror is 12 cm.