A radioactive substance has a half-life of 10^8 years and an activity of 10^4 ~Bq . The number of atoms of this substance present is

Step-by-step solution

Half-life of a radioactive substance, aligned T_ 1 / 2 & =10^8 years & =10^8 365 24 60 60=3.15 10¹⁵ ~s aligned Activity, R=10^4 ~Bq Let N be the number of atoms of substance, then we know that aligned R & = N =R / & = R 0.693 T_ 1 / 2 ( = 0.693 T_ 1 / 2 ) & = R T_ 1 / 2 0.693 = 10^4 3.15 10¹⁵ 0.693 & =4.54 10¹⁹ 4.5 10¹⁹ . aligned