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Four thousand active nuclei of a radioactive material are present at t = 0. After 60 minutes 500 active nuclei are left in the sample. The decay constant of the sample is

Options

  1. Aln 2 60 per minute
  2. Bln ⁡ 2 20 per minute
  3. C20 ln 2 per minute
  4. D60 ln 2 per minute

Correct answer

B. ln ⁡ 2 20 per minute

Step-by-step solution

60 minutes = 3 half lives ∴ T 1 2 = 20 m i n ∴ λ = ln 2 t 1 / 2 = ln ⁡ 2 20 p e r m i n

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