Two radioactive samples of different elements

PHYSICS · Single correct · A Level · Physics · Nuclear physics · Nuclear physics

Problem

Two radioactive samples of different elements, with half-lives

t_1

and

t_2

respectively, have the same number of nuclei at

t=0

. The time after which their activities are equal is (1)

\frac{t_1t_2}{0.693(t_2-t_1)}\ln\frac{t_2}{t_1}

(2)

\frac{t_1t_2}{0.693}\ln\frac{t_2}{t_1}

(3)

\frac{t_1t_2}{0.693(t_1+t_2)}\ln\frac{t_2}{t_1}

(4) None of these