Question

A 5 cm tall object is placed perpendicular to principal axis of a convex
lens of focal length 10 cm. If the object is placed 30 cm away from the
lens, find the position, size and nature of image.

Answer 1

given f=10cm
Therefore 2f will be at a distance of 20cm
Said that obj is 30 cm away from lens so it's position is beyond 2F
An obj placed beyond 2F in case of convex lens always gives a real;inverted and diminished image between F2 and 2F2
Hope it helps:)

Answer 2

Given :
height of object=h0=5cm
focal length of lens=10cm
object distance=-30cm after sign conventions.
image distance=?
By lens formula :
1/f=1/v-1/u
1/v=1/f+1/u
=1/10-1/30
=3-1/30
2/30
v=30/2= 15cm
magnification=m=v/u
m=15/-30 =-1/2= -0.5cm
m=hi/ho
hi=mxho
=-0.5x 5
= -2.5cms
Thus object is placed beyond C and image formed is in between F and c.
Inverted, real and diminished.