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Three lenses in contact have a combined ...

Three lenses in contact have a combined focal length of 12 cm. When the third lens is removed, the combined focal length is `(60)/(7)` cm. The third lens is

A

Aconverging lens of focal length 30 cm

B

Aconverging lens offocalelngth 60 cm

C

A diverging lens of focal length 30 cm

D

A diverging lens o f focal length 60 cm

Text Solution

Verified by Experts

The correct Answer is:
C
`1/f=1/(f_(1)) + 1/(f_(2)) + 1/(f_(3)), f=2cm,(f_(1)) + 1/(f_(2))=1/(60/7)`
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NARAYNA-RAY OPTICS AND OPTICAL INSTRAUMENTS -EXERCISE-2 (C.W)(REFRACTION THROUGH SPHERICAL SURFACES )
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