The java applet below demonstrates radioactive decay. Adjust your desired
parameters, then press start. Lambda is defined as the probability of a
decay per unit time for one atom.
(The unit time equals the timestep in the program.)
The system starts out with a initial number of atoms, after "start" is
pressed the system moves forward in unit time steps, shown on the right as bars.
In each turn all available atoms are cycled through; each atom is given
a chance to decay (marked as yellow) or remain (green). The expected
value or atoms, No*Exp[-lambda*t], is also shown. If your browser/java environment
is up to date, you should hear sound.
Here is the source and byte code for RadioDecay applet (compressed .jar file).