The ratio of parent to daughter isotopes in a radioactive decay process is 0.40. How many half- lives have elapsed since the material was 100% parent atoms?
A) more than 3
B) less than l
C) between 2 and 3
D) between l and 2

Question

Quizplus · Accepted Answer

The ratio of parent to daughter isotopes being 0.40 means that 40% of the original parent isotopes remain. This corresponds to slightly more than one half-life (where 50% remains) but less than two half-lives (where 25% remains), so it is between 1 and 2 half-lives.

The Ratio of Parent to Daughter Isotopes in a Radioactive