A lens of focal length 20 cm forms an inverted image at a distance 60 cm from the lens.
(i) Identify the lens.
(ii) How far is the lens present in front of the object ?
(iii) Calculate the magnification of the image.

Explanation

(i) Converx lens
(ii) `f=pm20cm,v=pm60cm`
`because1/f=1/v-1/u`
`rArr1/20=1/60-1/u`
`rArr1/u=1/60-1/20`
= `(1-3)/60=-2/60=-1/30`
`thereforeu=-30cm`
The lens is at a distance 30 cm in front of the object.
(iii) `m=v/u=(+60)/(-30)=-2` [-ve sign because image is real]