Question

An object is placed at a distance of 10 cm from a concave mirror of focal length 20 cm. 

Calculate the image distance.

Answer 1

 Image Distance-

Distance of the object from the mirror 'u' = −10 cm
Focal length of the concave mirror 'f' = −20 cm

We have to find the distance of the image 'v'.

Mirror Formula: 

`1/f=1/v+1/u` 

Therefore 

`1/(-20)=1/v+1/(-10)` 

`1/v=-1/20+1/10=-1/20+1/20` 

`1/v=1/20` 

v=20cm 

 Thus, the distance of the image 'v' is 20 cm.