Question

In a concave mirror The distance between mirror and object is 50cm while the distance between mirror and screen is 24cm. Find the focal length.

Answer 1

Given

Distance of the object, u = -50cm

Distance of the image, v = -24cm

To find

Focal length, (f)

By applying mirror's formula

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

$\mathsf{\implies\frac{1}{f} = \frac{1}{-50} + \frac{1}{-24}}$

$\mathsf{\implies\frac{1}{f} = \frac{-12 - 25}{600}}$

$\mathsf{\implies\frac{1}{f} = \frac{-37}{600}}$

$\mathsf{\implies f = \frac{-600}{37}}$

$\mathsf{\implies f= -16.216 \:cm}$

Therefore, the focal length is -16.216 cm