Question about Half life problem
We are performing an experiment using half-life =4.5 x 10^3 days labeled phenylalanine in which the five atomic hydrogens are labeled.To perform the experiment, the initial activity cannot be lower than 10% of the initial activity when the sample was received. Calculate How long after receiving the sample can you wait before performing the experiment?
Guidance: I know activity is proportional to concentration of the radioisotope.