The half-life of phosphorus-32 is 14.26 days. The decay constant is k=4.86×10−2/days. If you accidentally spill phosphorus-32 onto your shoe, how long would it take before 99.9% of the radioactive material has decayed so that you can safely wear the shoes again?

Question

The half-life of phosphorus-32 is 14.26 days. The decay constant is k=4.86×10−2/days.  If you accidentally spill phosphorus-32 onto your shoe, how long would it take before 99.9% of the radioactive material has decayed so that you can safely wear the shoes again?

bobpursley · Accepted Answer

.001=e^-.692t/th -.693*t/14.26 = ln .001 t= 142 days? check that.

DrBob222 · Answer

ln(No/N) = kt Substitute for No = 100 N = 100-99.9 Solve for t in days.

Anonymous · Answer

Yeah, thanks.