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Question 20258
JEE Physics · Medium

Ray Optics: Lens — Power of Combined System MCQ

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Lens — Power of Combined SystemMediumQuestion 20258

Question

A convex lens (P = +5 D) and a concave lens (P = −3 D) are placed in contact. Net power and focal length:
  1. A
    +2 D, 50 cm
    Correct
  2. B
    +8 D, 12.5 cm
  3. C
    −2 D, −50 cm
  4. D
    +2 D, 25 cm

Correct answer

+2 D, 50 cm

Explanation

P_total = P₁ + P₂ = 5 + (−3) = +2 D. f = 1/P = 1/2 m = 50 cm. The combination is a converging lens of 50 cm focal length.

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