Question

The half life of ${}_{58}Co$ is $72$ days. Its average life (in days) is,

• A. $104$
• B. $54$
• C. $205$
• D. $325$

Answer 1

The correct option is A $104$

Half life period $T_{1/2}=72$ days
Now, Average life is, $T_{av}=\frac{1}{\lambda }$ where, $\lambda$ is decay constant.
$T_{av}=\frac{T_{1/2}}{0.693}$ $(\because T_{1/2}=\frac{0.693}{\lambda })$

$T_{av}=\frac{72}{0.693}\approx 104$ days

Hence, $\left(A\right)$ is the correct answer.