If an object is placed 21 cm from a converging lens, the image formed is slightly smaller than the object. If the object is placed at a distance of 19 cm from the lens, the image formed is slightly larger than the object. The approximate focal length of the lens is:
If an object is placed 21 cm from a converging lens, the image formed is slightly smaller

Q. If an object is placed 21 cm from a converging lens, the image formed is slightly smaller than the object. If the object is placed at a distance of 19 cm from the lens, the image formed is slightly larger than the object. The approximate focal length of the lens is:

A.            20 cm

B.            18 cm

C.            10 cm

D.            5 cm

Answer: 10 cm
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