Question

The activity of a freshly prepared radioactive sample is `10^(10)` disintergrations per second, whose mean life is `10^(9)s`. The mass of an atom of this radioisotope is `10^(-25) kg`. The mass ( in `mg`) of the radioactive samples is

Answer 1

Correct Answer - `1`
`N=N_(0)e^(-lambdat)`
`(dN)/(dt)=10^(10)=N_(0)(lambda)e^(-10^(-9)t)`
at `(t=0)`
`10^(10)=N_(0)10^(-9)`
`N_(0)=10^(19)`
mass of sample `=N_(0)10^(-25)`
`=10^(-6)kgm`
`=10^(-6)xx10^(3)gm`
`10^(-3)gm`
`=1 mg`