RADIOACTIVITYDOE-HDBK-1019/1-93 Atomic and Nuclear PhysicsNP-01Page 34Rev. 0Example:A sample of material contains 20 micrograms of californium-252.Californium-252 has a half-life of 2.638 years.Calculate:(a)The number of californium-252 atoms initially present(b)The activity of the californium-252 in curies(c)The number of californium-252 atoms that will remain in 12 years(d)The time it will take for the activity to reach 0.001 curiesSolution:(a)The number of atoms of californium-252 can be determined as below.(b)First, use Equation (1-6) to calculate the decay constant.Use this value for the decay constant in Equation (1-3) to determine the activity.