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JEE Main 2025 (3 Apr, Shift 1) · Spherical Surfaces & Thin Lenses

Spherical Surfaces & Thin Lenses question from JEE Main 2025 (3 Apr, Shift 1)

Q19JEE Main 2025 · 3 APR · SHIFT 1Easy

Spherical Surfaces & Thin Lenses

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

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Answer: (c)

  1. 1f=(μ−1)(1R1−1R2)\frac{1}{f} = (\mu - 1)\left(\frac{1}{R_1} - \frac{1}{R_2}\right) with R1=10R_1 = 10, R2=−15R_2 = -15 cm.
  2. 112=(μ−1)(110+115)=μ−16\frac{1}{12} = (\mu - 1)\left(\frac{1}{10} + \frac{1}{15}\right) = \frac{\mu - 1}{6}
  3. μ−1=0.5⇒μ=1.5\mu - 1 = 0.5 \Rightarrow \mu = 1.5
  4. So the answer is (c) 1.5.
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