Question

An object is placed perpendicular to the principal axis of a convex lens of focal length 20 cm. The distance of the object from the lens is 30 cm. Find (i) the position (ii) the magnification and (iii) the nature of the image formed.

Answer 1

`1/f=1/v-1/u+>1/v=1/f+1/u=>v=(uxxf)/(u+f);f=20 cm, u=-30cm`

(i) `v=((-30)xx20)/(20-30)=60`cm

The image is formed at a distance of 60 cm on the other side of the optical centre

(ii) `m=-v/u=-60/(-30)=2`

(iii) Image formed is inverted.