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JAMB Physics 2002 Question 45

Question 45

Radioactivity and Nuclear Physics

The percentage of the original nuclei of a sample of a radioactive substance left after 5 half-lives is

  1. A.1%
  2. B.8%
  3. C.5%
  4. D.3%
Show the answer and explanation

Answer: D (3%)

Explanation

After 5 half-lives the fraction left is (½)5 = 1/32 ≈ 3.1%, which is about 3%.