For two successive decay processes, total activity (or number of disintegrations per second) is given by the green curve for :

,

where and are the decay constants for the two radioactive components (unstable nuclei or isotopes) and is the total number of nuclei at time . For example, if the first component is , with a half-life of 19.7 minutes and the second component is , with a half-life of 26 minutes, the decay constants are and , respectively.

In this Demonstration we use the relative values of radioactive constants with the "range without intersection".

The blue curve represents the second (or daughter) isotope :

.