Question
A $^{60}\textrm{Co}$ source is labeled 4.00 mCi, but its present activity is found to be $1.85\times 10^{7}\textrm{ Bq}$. (a) What is the present activity in mCi? (b) How long ago did it actually have a 4.00-mCi activity?
1. $0.500 \textrm{ mCi}$
2. $15.8 \textrm{ y}$
Solution Video