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JEE Main 2005 (AIEEE) · Law of Radioactive Decay

Law of Radioactive Decay question from JEE Main 2005 (AIEEE)

Q111JEE Main 2005 · AIEEEEasy

Law of Radioactive Decay

Starting with a sample of pure ${}^{66}Cu,\ \frac{7}{8}$ of it decays into $Zn$ in $15$ minutes. The corresponding half life is

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Answer: (d)

$\frac{7}{8}$ decayed means $\frac{1}{8}$ left, i.e. 3 half-lives.
$3T_{1/2} = 15\text{ min} \Rightarrow T_{1/2} = 5\text{ min}$ .
So the answer is (d) $5$ minutes.

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