Activity of a radioactive substance is R1 at time t1 and R2 at time t2(t2>t1). Then the ratio R2R1 is:
The half life of a ratio active source is T. If radio activities of the samples are R1−R2 at time
T1 and T2 Respectively, then the number of atoms disintegrated in time (T2−T1) is proportional to