The activity of a radioactive isotope falls to 12.5% in 90 days. Calculate the half life and decay constant.

Explanation

`N_(0)=100 N=12.5 t=90 days`
decay constant `lambda=(2.303)/(t) log (N_(0))/(N)`
`=0.02558 log 8`
`=2.311xx10^(-2) days^(-1)`
`t^(1//2)=(0.693)/(lambda)=(0.963)/(2.311xx10^(-2))=29.99 days`