Half-Life of a Radioactive Element
The half-life of a radioactive element is the time needed for half of the material to decay. The blue and orange points represent the original number of radioactive nuclei and those that decay; the number of blue points decreases by half at each step in time. The plot shows the population of radioactive nuclei at any time (in units).
Half-life is given by , where is the decay constant, the inverse of the mean lifetime of the radioactive isotope.