Answer to Question #87495 in Atomic and Nuclear Physics for Pranjal rawat

Question

Calculate the activity of K40 in 100kg man assuming that 0.35% of the body weight is potassium. The abundance of K40 is 0.012%, its half life is 1.31 109 years [ Avagadro number, N= 6.023 106] .

Answer 1

The number of atoms ⁴⁰K N = 6*10²³*350*12*10^-5/40 = 6.3*10²⁰, then the activity A = λN = 0.69*6.3*10²⁰/(1.31*10⁹*365*24*3.6*10³) = 1.05*10⁴ (s^-1).