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?

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