Write a formula showing the relation between half-life and average life of a radioactive substance.

(N/A) The half-life $(T_{1/2})$ of a radioactive substance is given by the formula: $T_{1/2} = \frac{\ln(2)}{\lambda} \approx \frac{0.693}{\lambda}$,where $\lambda$ is the decay constant.
The average life (or mean life,$\tau$) of a radioactive substance is given by the formula: $\tau = \frac{1}{\lambda}$.
By substituting $\lambda = \frac{1}{\tau}$ into the half-life formula,we get:
$T_{1/2} = 0.693 \times \tau$ or $T_{1/2} = \ln(2) \tau$.