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JEE Main 2021 (16 Mar, Shift 2) · Law of Radioactive Decay

Law of Radioactive Decay question from JEE Main 2021 (16 Mar, Shift 2)

Q61JEE Main 2021 · 16 MAR · SHIFT 2Medium

Law of Radioactive Decay

Calculate the time interval between 33% decay and 67% decay if half-life of a substance is 20 minutes.

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Answer: (d)

33% decay leaves 67%; 67% decay leaves 33%.
$\frac{67}{33} \approx 2$ , so the remaining amount halves: the gap is one half-life.
$\Delta t \approx 20$ min, so the answer is (d) 20 minutes.

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