Question

5. Where an object should be placed from a converging lens of focal length 20 cm, so as to obtain a real image of magnification 2? [Ans: u = - 30 cm]​

Answer 1

Answer:

The magnification of the image in a converging lens is 2.

⇒−vu=2⇒v=−2u.

The lens formula for a converging lens is 1v−1u=1f.

⇒−12u−1u=120⇒−32u=120

⇒u=−32×20=−30 cm.

⇒ The object should be placed at a distance of 30 cm from the mirror

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