A radioactive sample `S_1` having an activity of `5muCi` has twice the number of nuclei as another sample `S_2` which has an activity of `10muCi`. The half-lives of `S_1` and `S_2` can be

Options

A. `20` years and `5` years, respectively
B. `20` years and `10` years, respectively
C. `10` years each
D. `5` year each

Answer

A

Explanation

Activity `=lambdaN` & `T_(1//2)=(ln2)/lambda`
So `5=(ln2)/T_(1) (2N_(0))` & `10 =(ln2)/T_(2) (N_(0)) implies T_(1)=4T_(2)`