The radioactive or biological decay (e.g. by bacteria) is usually an exponential decay rate, which is described by the half-life.
The half-life T1/2 is the time in which an exponentially decreasing value has itself divided in half.
The half-life calculation is based on an exponential shape function.
With:
c0 = initial concentration
In the example the half-life is 5000 seconds.
The parameter t of the function is defined in the extended definitions – half-life (decay and production).
Equation of the mass transport