Isotope P decays to radioactive daughter D

PHYSICS · Subjective · A Level · Physics · Nuclear physics · Nuclear physics

Problem

Isotope P decays to radioactive daughter D, which then decays to a stable nucleus. The half-lives are

t_{1/2,P}=6.0\,\text{h}

and

t_{1/2,D}=2.0\,\text{h}

. At

t=0

the sample contains

1.0\times10^{18}

nuclei of P and none of D. Calculate the number of D nuclei present after

8.0\,\text{h}