A sample of radioactive element has a mass of $10 \mathrm{~g}$ at an instant $t=0$. The approximate mass of this element in the sample after two mean lives is:

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Aicharya · Accepted Answer

$\begin{aligned} & \mathrm{N}=\mathrm{N}_0 \mathrm{e}^{-\lambda \mathrm{t}} \Rightarrow \mathrm{m}=\mathrm{m}_0 \mathrm{e}^{-\lambda \mathrm{t}}=\mathrm{m}_0 \mathrm{e}^{-\lambda(2 / \lambda)} \ & =\frac{10}{\mathrm{e}^2}=1.35 \mathrm{gm}\end{aligned}$

A sample of radioactive element has a mass of $10 \mathrm{~g}$ at an instant $t=0$. The approximate mass of…

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