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JEE Main 2021 (20 Jul, Shift 2) · Law of Radioactive Decay

Law of Radioactive Decay question from JEE Main 2021 (20 Jul, Shift 2)

Q54JEE Main 2021 · 20 JUL · SHIFT 2Easy

Law of Radioactive Decay

A radioactive substance decays to $\left(\frac{1}{16}\right)^{th}$ of its initial activity in 80 days. The half life of the radioactive substance expressed in days is ____________.

Numerical answer type. Work it out, then open the answer.

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Answer: 20

$\left(\frac{1}{2}\right)^n = \frac{1}{16} \Rightarrow n = 4$ half-lives.
$4T = 80$ days $\Rightarrow T = 20$ days.
Half-life = 20 days.

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