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JAMB Physics 1987 Question 34

Question 34

Lenses and Optical Instruments

An object 3.0 cm high is placed 60.0 cm from a converging lens whose focal length is 20.0 cm. Calculate the size of the image formed.

  1. A.0.5 cm
  2. B.1.5 cm
  3. C.2.0 cm
  4. D.6.0 cm
Show the answer and explanation

Answer: B (1.5 cm)

Explanation

1/v = 1/20 − 1/60 = 1/30, so v = 30 cm. Magnification = 30/60 = ½, so the image is 1.5 cm high.