Question

What percentage of the atoms in a sample will remain undecayed in a time equal to mean life?

• A. 100%
• B. 63%
• C. 50 %
• D. 37 %

Answer 1

The correct option is D 37 %

Given :
time (t) = Mean life $t_{mean}=\frac{1}{\lambda }$
$\because N=N_0{e}^{-\lambda t}$
$N^{\prime }=N_0{e}^{-1}$
$\frac{N^{\prime }}{N_0}=\frac{1}{e}=0.37$.
$\frac{N^{\prime }}{N_0}=0.37\times 100=37\%$.