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The power of a combination of two lenses in contact is + 1.0 D. If the focal length of one of the lenses of the combination is + 20.0 cm, the focal length of the other lens would be :(a) -120.0 cm(b) +80.0 cm(c) -25.0 cm(d) -20.0 cm |
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Answer» Correct answer is (c) -25.0 cm We have : P = P1 + P2 \(1 = \frac{100}{20} + \frac{100}{f_2}\) \(-4 = \frac{100}{f_2}\) \(\Rightarrow f_2 = -25\,cm.\) |
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