Q. 13.7 A radioactive isotope has a half-life of T years. How long will it take the activity to reduce to a) 3.125%, b) 1% of its original value?
(a) The activity is proportional to the number of radioactive isotopes present
The number of half years in which the number of radioactive isotopes reduces to x% of its original value is n.
In this case
It will take 5T years to reach 3.125% of the original activity.
(b) In this case
It will take 6.64T years to reach 1% of the original activity.