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JEE Main 2025 (24 Jan, Shift 1) · Spherical Surfaces & Thin Lenses

Spherical Surfaces & Thin Lenses question from JEE Main 2025 (24 Jan, Shift 1)

Q23JEE Main 2025 · 24 JAN · SHIFT 1Easy

Spherical Surfaces & Thin Lenses

What is the relative decrease in focal length of a lens for an increase in optical power by 0.1 D from 2.5D? ['D' stands for dioptre]

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Answer: (a)

  1. f=1P⇒Δff=−ΔPPf = \frac{1}{P} \Rightarrow \frac{\Delta f}{f} = -\frac{\Delta P}{P}
  2. Relative decrease =0.12.5=0.04= \frac{0.1}{2.5} = 0.04
  3. So the answer is (a) 0.04.
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