Physics · Geometrical Optics

JEE Main 2024 — 4 April, Shift 1 — Question 39

An effective power of a combination of 5 identical convex lenses which are kept in contact along the principal axis is 25 D. Focal length of each of the convex lens is :

Option A:
20 cm
Correct
Option B:
50 cm
Option C:
500 cm
Option D:
25 cm

Answer: A

Step-by-step solution

We know that $\mathrm{P}_{\mathrm{eq}}=\Sigma \mathrm{P}_{\mathrm{i}}$

$\therefore$ given all lenses are identical

$\therefore 5 \mathrm{P}=25 \mathrm{D}$

$\therefore \mathrm{P}=5 \mathrm{D}$

$\therefore \frac{1}{\mathrm{f}}=5 \Rightarrow \mathrm{f}=\frac{1}{5} \mathrm{~m}=20 \mathrm{~cm}$

Answer key and solution verified before publishing.

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Exam: JEE Main 2024
Paper: 4 April, Shift 1
Subject: Physics
Chapter: Geometrical Optics
Topic: Lenses and Their Combinations, Silvering of Lens