A sample of a radioactive isotope is found to have an activity of 115.0 Bq immediately after it is pulled from the reactor that formed it. Its activity 2 h 15 min later is measured to be 85.2 Bq.
(a)
Calculate the decay constant and the half-life of the sample.
(b)
(b) How many radioactive nuclei were there in the sample initially

Question

A sample of a radioactive isotope is found to have an activity of 115.0 Bq immediately after it is pulled from the reactor that formed it. Its activity 2 h 15 min later is measured to be 85.2 Bq.
(a)
Calculate the decay constant and the half-life of the sample.
(b)
(b) How many radioactive nuclei were there in the sample initially

anonymous · Answer

a) I reckon it is (ln(85.2/115))/(135*60)
you can work out b) yourself.

eujc21 · Answer

I guess I was on the right path. so $$\lambda = ln(85.2/115)/8100s=.3.703*10^-5(units)$$