Question

A convex lens forms an image at 30 cm from lens on a screen.if the focal length of lens is 20 cm, find the distance at which the object is placed.​

Answer 1

Image distance, v=30cm

Focal length, f=20cm

Object distance, u=?

Using lens formula-

1/f=1/v-1/u

1/20=1/30-1/u

-1/u=1/20-1/30

-1/u=30-20/600

-1/u=10/600

-1/u=1/60

u=-60

so the object distance u=60cm.

Answer 2

Answer:

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