Which sample, A or B shown in the figure has shorter mean-life?
From the above figure, we get:
At t= 0,
(dN0/dt)A = (dN0/dt)B
as, dN/dt = -N
Therefore, (No)A = (No)B
Hence, at the beginning, there are the same numbers of radioactive atoms in both samples. Let, at any instant of time t,
(dN0/dt)A > (dN0/dt)B
or, A.NA = B.NB
or, Na > NB
or, B > A
We know, = 1/
So,
Here, sample B has a shorter mean life than sample A.