A biconvex glass lens has a focal length f an | vedclass

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(C) When a biconvex lens is cut along its principal axis (horizontal cut),each half has the same focal length $f$ as the original lens. This is becaus

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$2P$

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(C) When a biconvex lens is cut along its principal axis (horizontal cut),each half has the same focal length $f$ as the original lens. This is because the radius of curvature of the surfaces remains unchanged for each part. Thus,the power of each part remains $P = 1/f$. When these two parts are joined as shown in figure $(b)$,they form a combination of two lenses in contact. The total power of the combination is the sum of the powers of the individual lenses: $P_{net} = P_1 + P_2$. Since $P_1 = P$ and $P_2 = P$,the net power is $P_{net} = P + P = 2P$.

$A$ biconvex glass lens has a focal length $f$ and power $P$. It is cut into two symmetric parts along its principal axis. If these two parts are joined as shown in figure $(b)$,what is the new power of the combination?

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