Homer says that we can safely use nuclear power because all radioactive nuclei are gone after two half-lives. Marge says that only the decay rate is zero after two half-lives. Which one, if either, is correct, and why?
A) Homer, because half of the nuclei disintegrate in each half-life.
B) Marge, because the number of decays per unit time is halved in each half-life.
C) Homer, because it's safe to handle radioactive substances after two half-lives.
D) Both, because when all nuclei disintegrate the decay rate is also zero.
E) Neither, because one quarter of the nuclei are left after two half-lives.

Question

Quizplus · Accepted Answer

After one half-life, half of the original radioactive nuclei remain. After two half-lives, half of that remaining half (or one quarter of the original amount) still remains, not zero. The decay rate decreases but does not reach zero after two half-lives.

Homer Says That We Can Safely Use Nuclear Power Because