The half life of a radioactive sample is T. If the activities of the sample at time t1 and t2(t1<t2) are R1 andR2 respectively, the number of atoms disintegrated in time t2−t1 is proportional to,
A
(R1−R2)T
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B
(R1+R2)T
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C
R1R2R1+R2T
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D
R1+R2T
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Solution
The correct option is A(R1−R2)T
Activity or rate of decay is given by,
R=λN
⇒R1=λN1 and R2=λN2
R1−R2=λ(N1−N2)=0.693T(N1−N2)
N1−N2=T0.693(R1−R2)
⇒(N1−N2)∝(R1−R2)T
Here, (N1−N2) is the number of atoms disintegrated in the time interval (t1−t2)