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JAMB Physics 2002 Question 28

Question 28

Light and Reflection

A concave mirror of radius of curvature 40cm forms a real image twice as large as the object. The object distance is

  1. A.30cm
  2. B.40cm
  3. C.60cm
  4. D.10cm
Show the answer and explanation

Answer: A (30cm)

Explanation

f = 20 cm and v = 2u. 1/u + 1/(2u) = 1/20 gives 3/(2u) = 1/20, so u = 30 cm.