If `N_(0)` is the original mass of the substance of half - life period `t_(1//2) = 5 year` then the amount of substance left after `15` year is

Options

A. `(N_(0))/8`
B. `(N_(0))/16`
C. `(N_(0))/2`
D. `(N_(0))/4`

Answer

A

Explanation

`N_(0)` is the initial amount of substance and N is the amount left after decay. Then number nuclei left after successive disintegration is given by
`N=N_(0)(1/2)^(n)`
n= no. oif half lives `=1/(t_(1//2))=15/5=3`
Therefore `N=N_(0)(1/2)^(3)=(N_(0))/8`