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JEE Main20199 Jan 2019Morning ShiftPhysicsNuclear PhysicsActual

A Sample of radioactive material A , that has an activity of 10 m Ci 1 C i = 3.7 × 10 10 d e c a y s s - 1 , has twice the number of nuclei as another sample of a different radioactive material B which has an activity of 20 m Ci . The correct choices for half-lives of A and B would then be, respectively:

Options

  1. A5 days and 10 days
  2. B10 days and 40 days
  3. C20 days and 10 days
  4. D20 days and 5 days

Correct answer

D. 20 days and 5 days

Step-by-step solution

Activity A = λ N 10 = λ A N A 20 = λ B N B 1 2 = λ A λ B 2 λ A λ B = 1 4   ⇒ T A T B = 4 1

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