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JAMB Physics 1989 Question 47

Question 47

Modern Physics

When a radiation strikes a metal surface, electrons may be ejected from the metal. The maximum kinetic energy which may be acquired by an ejected electron depends on the

  1. A.intensity of the radiation
  2. B.source of the radiation
  3. C.wavelength of the radiation
  4. D.detection device for the electron.
Show the answer and explanation

Answer: C (wavelength of the radiation)

Explanation

By Einstein's equation, maximum KE = hf − W = hc/λ − W, so it depends on the wavelength (frequency). Intensity only changes how many electrons come out.