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JEE Main 2020 (7 Jan, Shift 2) · Law of Radioactive Decay

Law of Radioactive Decay question from JEE Main 2020 (7 Jan, Shift 2)

Q76JEE Main 2020 · 7 JAN · SHIFT 2Medium

Law of Radioactive Decay

The activity of a radioactive sample falls from 700 s–1 to 500 s–1 in 30 minutes. Its half life is close to:

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Answer: (a)

  1. λ=1tln⁡A0A=130ln⁡700500=0.33630≈0.0112 min−1\lambda = \frac{1}{t}\ln\frac{A_0}{A} = \frac{1}{30}\ln\frac{700}{500} = \frac{0.336}{30} \approx 0.0112\text{ min}^{-1}.
  2. T=0.6930.0112≈62T = \frac{0.693}{0.0112} \approx 62 min.
  3. So the answer is (a) 62 min.
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