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KVPY2017PhysicsRay Optics

A point source of light is placed at 2 from a converging lens of focal length f. A flat mirror is placed on the other side of the lens at a distanc d such that rays reflected from the mirror are parallel after passing through the lens again. If f=30 ~cm , then d is equal to

Options

  1. A15 ~cm .
  2. B30 ~cm .
  3. C45 ~cm .
  4. D75 ~cm .

Correct answer

C. 45 ~cm .

Step-by-step solution

at 2 f - object then image will also be at ' 2 f '. Finally image is at therefore after reflection from mirror. Image must be formed at focus. d= f+2 f 2 =45 ~cm

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