The half life of `Ra` is 1600 years. The fraction of a sample of `Ra` that would remain after 6400 years is

Options

A. `1//16`
B. `1//4`
C. `1//8`
D. `1//2`

Answer

A

Explanation

`t_(1//2) = 1600` min, `T = 6400` min
Number of half lives `= (6400)/(1600) = 4`
We know that `N = ((1)/(2))^(n) N_(0)`
or `(N)/(N_(0)) = ((1)/(2))^(n) = ((1)/(2))^(4) = (1)/(16)`