Question

Calculate the distance of an object of height h from a concave mirror of radius of curvature 20 cm, so as to obtain a real image of magnification 2. Find the location of the image also.

Answer 1

Given: Radius of curvature of mirror = 20 cm

 ∴ Focal length of mirror, f = −10 cm

Since the image is real,
Magnification of image, m = −2

`m=-v/u`

`=>-2=-v/u`

`=>v=2u`

Using mirror formula,

`1/f=1/v+1/u=1/(2u)+1/u=3/(2u)`

`=>u=3/2 f=3/2xx(-10)=-15cm`

∴v=2u=−30 cm

Therefore, the distance of the object is 15 cm in front of the mirror and the position of the image is 30 cm in front of the mirror.