The decay constant λ, the half life \(T_{\frac{1}{2}}\) and the mean life τ of a radioactive nucleus are related as:
1
\(\tau = \dfrac{1}{\lambda}\ ; \ T_{\frac{1}{2}} = 0.693 \ \lambda\)
2
\(\tau = \dfrac{1}{\lambda} \ ; \ T_{\frac{1}{2}}=\tau . \ln 2\)
3
\(\tau = \dfrac{\ln 2}{\lambda} \ ; \ T_{\frac{1}{2}} = \tau . \ln 2\)
4
\(\tau = \lambda . \ln 2 \ ; T_{\frac{1}{2}} = \dfrac{\ln 2}{\lambda}\)