Q 12-13-020NEETJEE MainTop questionMedium
What fraction of a radioactive sample remains after one mean life?
Answer: (C) $\dfrac{1}{e}$
$N = N_0e^{-\lambda t}$ with $t = \tau = \dfrac{1}{\lambda}$: $\dfrac{N}{N_0} = e^{-1} \approx 0.37$.
Solution by Sreeraj P, M.Sc Physics