In a laboratory experiment, the activity of a pure radioactive sample fell from 6.4×104Bq to 2.5×104Bq in 90minutes.
(i) Derive an expression for the half-life of a radionuclide in terms of two measured activities A1 (at time t1) and A2 (at time t2), where t2>t1.
(ii) Using your derived expression, determine the half-life of the sample in minutes.
(iii) Calculate the additional time required for the activity to fall to 5.0×103Bq.