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COMEDK2016PhysicsRay Optics

Two co-axial lenses of power +4 D and -2 D are placed in contact. The focal length of combination is

Options

  1. A0.5 ~m
  2. B0.25 ~m
  3. C0.16 ~m
  4. D-0.5 ~m

Correct answer

A. 0.5 ~m

Step-by-step solution

The focal length of combination of two lenses, aligned 1 f &= 1 f₁ + 1 f₂ = 1 (1 / 4) + 1 (-1 / 2) (f= 1 P ) &=4-2=2 f &=0.5 ~m aligned

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