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JAMB Physics 1994 Question 33

Question 33

Light and Reflection

To produce a parallel beam of light from a concave mirror, the distance at which the lamp should be placed from the mirror is equal to

  1. A.the focal length
  2. B.two times the focal length
  3. C.the distance of the image
  4. D.two times the radius of curvature
Show the answer and explanation

Answer: A (the focal length)

Explanation

Rays from a lamp at the principal focus are reflected parallel to the principal axis (as in a torch).