Question

A convex lens of a focal length 10cm produces a real image 3 times magnified.Find the object distance

Answer 1

Gn convex lens so f=+10cm

And m=v/u=-3 as it is real and inverted

v=-3u.....(1)

1/v-1/u=1/f

-1/3u-1/u=1/10

-1-3/3u=1/10

-4/3u=1/10

u=-40/3=-13.33cm

Substituting u in (1)

v=-3×-40/3=40cm

Object distance =u=-13.33cm