A radioactive substance has a half life of `60` minutes. After `3` hours, the fraction of atom that have decayed would be.

Options

A. `12.5%`
B. `87.5%`
C. `8.5%`
D. `25.1%`

Answer

B

Explanation

Half - life = 60 minutes
In time 3 hours, number of half - time, n = 3.
We know that, `N=N_(0)((1)/(2))^(n) rArr (N)/(N_(0)) =((1)/(2))^(3)=(1)/(8)`
`therefore" The fraction of substance left after 3 hours is 1/8"`.
`therefore" The fraction decayed "=1-(1)/(8)=(7)/(8)=87.5%`