Question

The half-life of ${}^{131}I$ is $8$ days. Given a sample of ${}^{131}I$ at time $t=0$, we can assert that

• A. no nucleus will decay before $t=4$ days
• B. no nucleus will decay before $t=8$ days
• C. all nuclei will decay before $t=16$ days
• D. a given nucleus may decay at any time after $t=0$

Answer 1

The correct option is D a given nucleus may decay at any time after $t=0$

At time $t=0$, the nuclei starts to decay and at any time after that some of the nuclei may have decayed.

Up to time $t=8days$, about half the initial number of the nucleus have decayed and up to $16days$, only one-fourth of the initial number of the nucleus are left undecayed.