Question

A concave mirror produces three times magnified image on a screen. If the object is placed 20 cm in front of the mirror, how far is the screen from the object.

Answer 1

Here,
Magnification, m = - 3 (As the image is real)

Object distance, u = - 20 cm
Image distance, v = ?

We know, `m=−v/u`
`−3=−(v/(−20))`

`⇒v=−60 cm`

The screen is placed in front of the mirrors at a distance of 60 cm from the pole of the mirror.

Thus, the screen is placed 40 cm (= 60 cm - 20 cm) away from the object.