A sample of a radioactive element has a mass of `10 g` at an instant `t=0`. The approxiamte mass of this element in the sample after two mean lives is .

Options

A. `10//e^(2)`
B. `10//e`
C. 10e
D. e/10

Answer

A

Explanation

Activity, `A=(-dN)/(dt)=lamdaN`
As the number of nuclei (N) per mole are equal for both the substances, inrespective of their molecular mass, therefore
`Aproplamda,(A_(1))/(A_(2)) =(lamda_(1))/(lamda_(2))=(4)/(3)`