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(A) The effective focal length $F$ of two thin lenses in contact is given by the formula $\frac{1}{F} = \frac{1}{f_1} + \frac{1}{f_2}$.For a convex le

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behaves as a concave lens if $|f_{	ext{convex}}| > |f_{	ext{concave}}|$

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(A) The effective focal length $F$ of two thin lenses in contact is given by the formula $\frac{1}{F} = \frac{1}{f_1} + \frac{1}{f_2}$.For a convex lens, $f_1 > 0$, and for a concave lens, $f_2 Substituting these values, we get $\frac{1}{F} = \frac{1}{f_{	ext{convex}}} - \frac{1}{|f_{	ext{concave}}|} = \frac{|f_{	ext{concave}}| - f_{	ext{convex}}}{f_{	ext{convex}} |f_{	ext{concave}}|}$.If $|f_{	ext{concave}}| If $|f_{	ext{concave}}| > f_{	ext{convex}}$, then $\frac{1}{F} > 0$, which implies $F > 0$, meaning the combination behaves as a convex lens.Therefore, the combination behaves as a concave lens if $|f_{	ext{convex}}| > |f_{	ext{concave}}|$.

$A$ thin convex lens and a thin concave lens are kept in contact and are co-axial. Which of the following statements is correct for this combination of two lenses?

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