The decay constant of radio isotope is `lambda`. If `A_(1) and A_(2)` are its activities at times `t_(1) and t_(2)` respectively, the number of nuclei which have decayed during the time `(t_(1)-t_(2))`

Options

A. `A_(1)t_(1)- A_(2) t_(2)`
B. `A_(1)- A_(2)`
C. `(A_(1) - A_(2))//lamda`
D. `lamda (A_(1)- A_(2))`

Answer

C

Explanation

`A_(1)= lamda N_(1), A_(2)= lamda N_(2)`
`A_(1)- A_(2)= lamda (N_(1)- N_(2)) rArr N_(1)- N_(2) = (A_(1)- A_(2))/(lamda)`