Question

An object of height 4cm is placed at a distance of 30cm in a convex lens of focal length 2ocm find the ratio of size of image to size of object

Answer 1

the question has been already answered by me.

u = -30 cm
f = 20cm
h= 4 cm.

1/v- 1/u = 1/f
1/v= 1/20-1/30
= (3-2)/ 60
1/v = 1/60
v= 60 cm.

m=v/u = h'/h
60/-30= h' / 4
-2 = h'/4
h' = -8

ratio : -2:1