A sample of radioactive material A, that has an activity of 10 mCi (1 Ci = 3.7 x 1010 decays/s), has twice the number of nuclei as another sample of a different radioactive material B which has an activity of 20 mCi. The correct choices for half-lives of A and B would then by respectively :
5 days and 10 days
10 days and 40 days
20 days and 5 days
20 days and 10 days
Law of radioactivity -
- wherein
Ratio of disintegration is propotional to number of nuclei
= disintegration constant
Activity A =
For A , A = 2 No = 10
For B , A = No = 20
= 4
So option 20 days and 5 days satisfies this condition .
5 days and 10 days
Option 2)10 days and 40 days
Option 3)20 days and 5 days
Option 4)20 days and 10 days
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