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JAMB Physics 1984 Question 48

Question 48

Modern Physics

Which of the following statements is (are) NOT true about the emission of photoelectrons from metallic surfaces? I. All metallic surfaces emit the same number of photoelectrons in a given light II. Most metallic surfaces emit the same number of photoelectrons in visible and infrared light. III. A metallic surface emits photoelectrons only if the frequency of the incident light is higher than its own characteristic threshold frequency

  1. A.I only
  2. B.II only
  3. C.I and II
  4. D.II and III
  5. E.III only
Show the answer and explanation

Answer: C (I and II)

Explanation

III is the threshold-frequency rule and is true. Different metals emit differently (I false), and most metals emit no photoelectrons at all in visible or infrared light (II false).