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JAMB Physics 2003 Question 23

Question 23

Light and Reflection

At what position will an object be placed in front of a concave mirror in order to obtain an image at infinity?

  1. A.At the pole of the mirror
  2. B.At the principal focus
  3. C.At the centre of curvature
  4. D.Between the principal focus and the centre of curvature.
Show the answer and explanation

Answer: B (At the principal focus)

Explanation

Rays from an object at the principal focus leave the concave mirror parallel, so the image is at infinity.