Two radioactive materials $A$ and $B$ have decay constants $10 \lambda$ and $\lambda$, respectively.

Question

Two radioactive materials $A$ and $B$ have decay constants $10 \lambda$ and $\lambda$, respectively. If initially they have the same number of nuclei, then the ratio of the number of nuclei of $A$ to that of $B$ will be $\frac{1}{e}$ after a time

Professor PC Thomas Classes · Answer

Ratio $e^{-(10\lambda - \lambda)t} = \frac{1}{e}$ gives $t = \frac{1}{9\lambda}$.