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JAMB Physics 2007 Question 3

Question 3

Dispersion of Light and Colours

The production of pure spectrum could easily be achieved using a

  1. A.triangular prism only.
  2. B.triangular prism with two concave lenses.
  3. C.triangular prism with two convex lenses.
  4. D.glass prism with a pin.
Show the answer and explanation

Answer: C (triangular prism with two convex lenses.)

Explanation

A pure spectrum needs a parallel beam entering the prism (first convex lens) and the separated colours focused sharply on a screen (second convex lens).