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JAMB Physics 2015 (CBT) Question 7

Question 7

Lenses and Optical Instruments

If a document is to be produced using a duplicating camera, where should the document be placed in order to obtain an exact copy?

  1. A.At the point which is twice the focal length of the lens of the camera.
  2. B.At the optical centre of the lens of the camera.
  3. C.Between the principal focus and a point twice the focal length of the lens of the camera.
  4. D.Beyond a point twice the focal length of the lens
Show the answer and explanation

Answer: A (At the point which is twice the focal length of the lens of the camera.)

Explanation

An object at 2F of a converging lens gives a real image at 2F on the other side, the same size as the object, so the copy is exact.