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MHT CET 2025 (21 Apr, Shift 1) · Law of Radioactive Decay

Law of Radioactive Decay question from MHT CET 2025 (21 Apr, Shift 1)

Q18MHT CET 2025 · 21 APR · SHIFT 1Medium

Law of Radioactive Decay

Two radioactive materials AA and BB having decay constant ' 7λ7\lambda ' and ' λ\lambda ' respectively, initially have same number of nuclei. The time taken to have the ratio of number of nuclei of material B to that of A as ' e ' is

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Answer: (b)

  1. NBNA=e−λte−7λt=e6λt\frac{N_B}{N_A} = \frac{e^{-\lambda t}}{e^{-7\lambda t}} = e^{6\lambda t}.
  2. e6λt=e⇒t=16λe^{6\lambda t} = e \Rightarrow t = \frac{1}{6\lambda}.
  3. So the answer is (b) 16λ\frac{1}{6\lambda}.
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