A certain radioactive element disintegrates for an interval of time equal to mean life. What fraction of element disappears? What fraction of element is left?

Explanation

Average life, `T_(alpha)=1/lamda`
Now, `N=N_(0)e^(-lamdat)`
When `t=T_(alpha)`, then `N=N_(0)e^(-lamdaxx1/lamda)=N_(0)e^(-1)=1/eN_(0)`
or `N/N_(0)=1/6=1/(2.718)=0.368`
So, the fraction of the element left behind is 0.368. The fraction of the element which disappear = 1 - 0.368 = 0.368.