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CUET · PHYSICS · PYQ PAPER 2025

An eye specialist prescribes spectacles having a combination of a converging lens of focal length 25 cm and a diverging lens of focal length of 20 cm. The power of the combination of two lenses (in dioptre) is

  1. A 1
  2. B -1
  3. C 1.1
  4. D 2
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Answer & Solution

Correct Answer

(B) -1

Step-by-step Solution

Detailed explanation

\(P_1 = \frac{1}{f_1} = \frac{1}{0.25 \text{ m}} = 4 \text{ D}\) \(P_2 = \frac{1}{f_2} = \frac{1}{-0.20 \text{ m}} = -5 \text{ D}\) \(P_{total} = P_1 + P_2 = 4 \text{ D} + (-5 \text{ D}) = -1 \text{ D}\)
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