Physics · Geometrical Optics

JEE Main 2026 — 23 January, Evening Shift — Question 43

The size of the images of an object, formed by a thin lens are equal when the object is placed at two different positions 8 cm and 24 cm from the lens. The focal length of the lens is $\_\_\_\_$ cm .

Answer: 16

Numerical answer — enter this value.

Step-by-step solution

$m=\frac{f}{f+u}$ $\mathrm{m}_{1}=-\mathrm{m}_{2}$ $\frac{\mathrm{f}}{\mathrm{f}-8}=-\frac{\mathrm{f}}{\mathrm{f}-24}$ $\mathrm{f}-8=24-\mathrm{f}$ $2 \mathrm{f}=32$ $\mathrm{f}=16 \mathrm{~cm}$

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Exam: JEE Main 2026
Paper: 23 January, Evening Shift
Subject: Physics
Chapter: Geometrical Optics
Topic: Lenses and Their Combinations, Silvering of Lens

A prism of angle 75^circ and refractive index √(3) is coated with thin film of refractive index 1.5 only at the back exit surface. To have…

Answer: 16

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