A convex lens of focal length A and a concave | vedclass

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(C) For two thin lenses in contact,the equivalent focal length $F$ is given by the formula: $\frac{1}{F} = \frac{1}{F_1} + \frac{1}{F_2}$.Given,the fo

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$\frac{AB}{B - A}$

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(C) For two thin lenses in contact,the equivalent focal length $F$ is given by the formula: $\frac{1}{F} = \frac{1}{F_1} + \frac{1}{F_2}$.Given,the focal length of the convex lens is $F_1 = A$ (positive) and the focal length of the concave lens is $F_2 = -B$ (negative).Substituting these values into the formula:$\frac{1}{F} = \frac{1}{A} + \frac{1}{-B}$$\frac{1}{F} = \frac{1}{A} - \frac{1}{B}$$\frac{1}{F} = \frac{B - A}{AB}$Therefore,the focal length of the combination is $F = \frac{AB}{B - A}$.

$A$ convex lens of focal length $A$ and a concave lens of focal length $B$ are placed in contact with each other. The focal length of this combination is ......

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