The half - life of `^(215) At` is `100 mu , s.`The time taken for the radioactivity of a sample of `^(215) At` to decay to `1//16^(th)` of its initially value is

Options

A. `400mu sec`
B. `6.3 mu sec`
C. `40mu sec`
D. `300mu sec`

Answer

A

Explanation

`A = A_(0)((1)/(2))^(n) rArr (A)/(A_(0))= ((1)/(2))^(n)`
`(1)/(16) = ((1)/(2))^(4) = ((1)/(2))^(n)`
`n = 4`
`t = nT_(1//2) = 4xx100 = 400mu sec`