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Physics · Geometrical Optics

JEE Main 2025 — 3 April, Morning Shift — Question 60

The radii of curvature for a thin convex lens are 10 cm and 15 cm respectively. The focal length of the lens is 12 cm . The refractive index of the lens material is

  1. Option A:

    1.5

    Correct
  2. Option B:

    1.2

  3. Option C:

    1.4

  4. Option D:

    1.8

Answer: A

Step-by-step solution

For biconvex R1=10R2=15\begin{aligned} & R_{1}=10 & R_{2}=15 \end{aligned}

1f=(μ−1)(1R1+1R2)\frac{1}{f}=(\mu-1)\left(\frac{1}{R_{1}}+\frac{1}{R_{2}}\right)

112=(μ−1)(110+115)=(μ−1)(16)\frac{1}{12}=(\mu-1)\left(\frac{1}{10}+\frac{1}{15}\right)=(\mu-1)\left(\frac{1}{6}\right)

μ−1=12⇒μ=1.5\mu-1=\frac{1}{2} \Rightarrow \mu=1.5

Answer key and solution verified before publishing.

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Exam
JEE Main 2025
Paper
3 April, Morning Shift
Subject
Physics
Chapter
Geometrical Optics
Topic
Lenses and Their Combinations, Silvering of Lens

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