**PURPOSE: **To illustrate the radioactive decay of a sample of nuclei and to show how a half-life is determined in an actual radioactive decay experiment.

**DESCRIPTION: **Thirty dice with holes along one axis represent radioactive nuclei. When the dice are rolled on the overhead projector, a certain number will have the hole showing, meaning that they have decayed. They are collected and placed on a transparency graph showing how the sample would decay theoretically. The remaining dice are rolled, and the decayed nuclei placed on the graph in the next horizontal location. The procedure is repeated until every die has decayed.

The "half life" is the number of times the dice must be thrown until only half are left, where each throw represents a certain fixed time interval. If you want to get real fancy, you can make use of the fact that you actually expect one-third of the dice to decay in any throw.

**SUGGESTIONS: **

**REFERENCES: ** (PIRA 7D10.50)

**EQUIPMENT: **Thirty non-radioactive dice with holes, transparency graph.

**SETUP TIME: **None.