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What is the focal length of a convex lens of focal length 30 cm in contact with a concave lens of focal length 20 cm? Is the system a converging or a diverging lens? Ignore thickness of the lenses. |
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Answer» Solution :Here, `f_(1) = +30 CM` and `f_(2) = -20 cm` `THEREFORE 1/f = 1/f_(1) + 1/f_(2) = 1/30 + 1/(-20) =(2-3)/60 = -1/60 rArr f=-60 cm` `-ve` sign shows that the system is a diverging lens |
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