Two identical symmetric double convex lenses of focal length f are cut into two equal parts L 1 , L 2 by AB plane and L 3 , L 4 by XY plane as shown in figure respectively. The ratio of focal lengths of lenses L 1 and L 3 is

Physics · Geometrical Optics

JEE Main 2025 — 29 January, Evening Shift — Question 23

Two identical symmetric double convex lenses of focal length $f$ are cut into two equal parts $\mathrm{L}_{1}, \mathrm{~L}_{2}$ by AB plane and $L_{3}, L_{4}$ by XY plane as shown in figure respectively. The ratio of focal lengths of lenses $L_{1}$ and $L_{3}$ is

Option A:
$1: 4$
Option B:
$1: 1$
Option C:
$2: 1$
Option D:
$1: 2$
Correct

Answer: D

Step-by-step solution

$f_{L_{1}}=f_{L_{2}}=f$

$\mathrm{f}_{\mathrm{L}_{3}}=\mathrm{f}_{\mathrm{L}_{4}}=2 \mathrm{f}$

$\therefore \mathrm{f}_{\mathrm{L}_{1}}: \mathrm{f}_{\mathrm{L}_{3}}=1: 2$

Answer key and solution verified before publishing.

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Exam: JEE Main 2025
Paper: 29 January, Evening Shift
Subject: Physics
Chapter: Geometrical Optics
Topic: Experiments for Determination of Focal Length of Lens & Mirrors

Answer: D

Step-by-step solution

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