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NEET 2023 · Combination of Lenses

Combination of Lenses question from NEET 2023

Q32NEET 2023Easy

Combination of Lenses

Two thin lenses are of same focal lengths $(f)$ , but one is convex and the other one is concave. When they are placed in contact with each other, the equivalent focal length of the combination will be:

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Answer: (c)

$\frac{1}{F} = \frac{1}{f_1} + \frac{1}{f_2}$ with $f_1 = +f$ , $f_2 = -f$ .
$\frac{1}{F} = \frac{1}{f} - \frac{1}{f} = 0 \Rightarrow F = \infty$
So the answer is (c) Infinite.

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