The count rate of nuclear radiation coming from a radioactive sample containing 128I varies with time as follows.
(a) Plot ln(R0/R) against t.
(b) From the slope of the best straight line through the points, find the decay constant λ.
(c) Calculate the half-life t1/2.
We take R˳ at time t=t˳ i.e. R˳= 30× 109 s-1
(a)
(b) As ln(R0/R) = λt
So, slope of this curve will give the value of λ
∴
(c)