Question

the image formed on a screen by a concave mirror of radius 20 cm is 3 times the size of the object. what is the distance of the screen from the mirror?​

Answer 1

Given that,

Radius of mirror = 20 cm

Size of image = 3 times of size of object

We need to calculate the distance of the screen from the mirror

Using formula of magnification

`m=-(h')/(h)=(v)/(u)`

`-(h')/(h)=(v)/(u)`

Where, h' = size of image

h = size of object

v = image distance from mirror

u = object distance from mirror

Put the value into the formula

`-(3h)/(h)=(-v)/(u)`

`(3)/(1)=(v)/(u)`

`v=3u`

The distance of image will three times of object distance.

Hence, The distance of the screen from the mirror is 3u.