Question

Probability of the remains active of a nucleus in one mean life is _____.

Answer 1

Probability of survival of remains of radio active nucleus for time t,

$P\left(active\right)=\frac{N}{N_0}=e^{-\lambda t}t=\frac{1}{\lambda }P\left(active\right)=e^{-\lambda \frac{1}{\lambda }}=e^{-1}=\frac{1}{e}$