Question

A 1 cm high object is placed at a distance of 32 cm from a concave mirror. The image is real, inverted and 1.5 cm in size. Calculate the focal length of the mirror and the position of the image.

Answer 1

u = -32 cm

$h_o$ = 1cm

$h_i$ = -1.5

$\frac{h_i}{h_o}$ = $\frac{-v}{u}$

$\frac{-1.5}{1}$ = $\frac{-v}{-32}$

v = -48 cm

Image is 48 cm from the pole and on the same side of the object

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

$\frac{1}{f}$ =$\frac{1}{f}$ - $\frac{1}{32}$

f = -19.2 cm

Focal length of the mirror is 19.2 cm