If `m g` of a radioactive species (molar mass `M)` has decay constant `lambda` The specis activity of sample at `t = ` is given by:

Options

A. `((m N_(A))/(M)) e ^(- lamda t)`
B. `((m N _(A) lamda )/(M)) e ^(- lamda t)`
C. `((mN_(A))/(Mlamda )) e ^(- lamda t)`
D. `(m)/(lamda ) (1- e ^(-lamda t ))`

Answer

B

Explanation

activity `= lamda N _(0) e ^(- lamda t)` where `N_(0) = (N_(A)m)/(M)`