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CUET · PHYSICS · PYQ PAPER 2025

A thin lens L1 of focal length 20 cm placed in combination with another thin lens L2 acts as a lens of focal length 12.5 cm. The power of L2 is

  1. A 3 D
  2. B 8 D
  3. C 5 D
  4. D 1 D
Verified Solution

Answer & Solution

Correct Answer

(A) 3 D

Step-by-step Solution

Detailed explanation

\(f_1 = 20 \text{ cm} = 0.2 \text{ m}\) \(f_{eq} = 12.5 \text{ cm} = 0.125 \text{ m}\) \(P_{eq} = P_1 + P_2\) \(\frac{1}{f_{eq}} = \frac{1}{f_1} + P_2\) \(P_2 = \frac{1}{0.125 \text{ m}} - \frac{1}{0.2 \text{ m}}\) \(P_2 = 8 \text{ D} - 5 \text{ D}\) \(P_2 = 3 \text{ D}\)