The half life period of radioactive element x is same as the mean life time of another radioactive element y. Initially they have the same number of atoms. Then:
(A) x and y have same decay rate initially and later on different decay rate.
(B) x and y decay at the same rate always.
(C) x will decay faster than y.
(D) y will decay faster than x.
Solution
Given, ${({t_{1/2}})_x} = {({t_{mean}})_y}$
$\therefore \frac{{0.693}}{{{\lambda _x}}} = \frac{1}{{{\lambda _y}}}$
$ \Rightarrow {\lambda _x} = 0.693{\lambda _y}$
$ \Rightarrow {\lambda _x} < {\lambda _y}$
If N is same, $A \propto \lambda $
$\therefore A_x < A_y $
Answer: (D)
