College Physics 10th Edition by Raymond Serway,Chris Vuille

Exercise 40

In a piece of rock from the Moon, the 87 Rb content is assayed to be 1.82 × 10 10 atoms per gram of material and the 87 Sr content is found to be 1.07 × 10 9 atoms per gram. (The relevant decay is 87 Rb 87 Sr + e . The half-life of the decay is 4.8 × 10 10 yr.) (a) Determine the age of the rock. (b) Could the material in the rock actually be much older (c) What assumption is implicit in using the radioactive-dating method