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CUET · PHYSICS · PYQ PAPER 2025

A converging lens and a diverging lens of equal focal lengths are placed coaxially in contact. The focal length and power of this combination will be

  1. A Focal length \( (F_c) = 0 \); power of combination \( (P_c) = 0 \)
  2. B Focal length \( (F_c) = \infty \); power of combination \( (P_c) = 0 \)
  3. C Focal length \( (F_c) = 0 \); power of combination \( (P_c) = \infty \)
  4. D Focal length \( (F_c) = \infty \); power of combination \( (P_c) = \infty \)
Verified Solution

Answer & Solution

Correct Answer

(B) Focal length \( (F_c) = \infty \); power of combination \( (P_c) = 0 \)

Step-by-step Solution

Detailed explanation

Converging lens focal length: \(f_1 = f\) Diverging lens focal length: \(f_2 = -f\) Equivalent focal length: \( \frac{1}{F_c} = \frac{1}{f_1} + \frac{1}{f_2} = \frac{1}{f} + \frac{1}{-f} = 0 \) \(F_c = \infty\) Power of combination: \(P_c = \frac{1}{F_c} = \frac{1}{\infty} = 0\)