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

After every half - life the mass of the substance reduces to half its initial value .
`N_(0) overset(5 "years") (to) (N_(0))/(2) overset("5 years")(to) (N_(0) //2)/(2)`
`= (N_(0))/(4) overset(5 "years")(to) (N_(0) //4)/(2) = (N_(0))/(8)`