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JAMB Physics 2009 Question 33

Question 33

Light and Reflection

Calculate the position of an object placed in front of a convex mirror having focal length of 12cm such that an image is formed 6cm away from the mirror.

  1. A.4.0 cm.
  2. B.3.0 cm.
  3. C.12.0 cm.
  4. D.9.0 cm.
Show the answer and explanation

Answer: C (12.0 cm.)

Explanation

With real-is-positive signs, f = −12 cm and v = −6 cm (virtual). 1/u = 1/f − 1/v = −1/12 + 1/6 = 1/12, so u = 12 cm.