Q 12-09-064JEE MainJEE Main 2025 (22 Jan, Shift 2)Easy
A symmetric thin biconvex lens is cut into four equal parts by two planes $AB$ and $CD$ as shown in the figure. If the power of the original lens is $4\ \text{D}$, then the power of a part of the divided lens is
Answer: (C) $2\ \text{D}$
The cut $CD$ is along the plane of the lens, splitting it into two identical plano-convex lenses. The original power is shared equally between them: $4\ \text{D} = P + P$, so each has $P = 2\ \text{D}$.
The cut $AB$ is along the principal axis. It only reduces the aperture of each piece; the curvature is unchanged, so the power stays $2\ \text{D}$.
Solution by Sreeraj P, M.Sc Physics