Modern Physics 3 Question 8

8. A radioactive sample S1 having an activity of 5μCi has twice the number of nuclei as another sample S2 which has an activity of 10μCi. The half lives of S1 and S2 can be

(a) 20yr and 5yr, respectively

(2008,3M)

(b) 20yr and 10yr, respectively

(c) 10yr each

(d) 5 yr each

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Solution:

  1. Activity of S1=12 (activity of S2 )

or λ1N1=12(λ2N2)

or λ1λ2=N22N1

or T1T2=2N1N2T= half - life =ln2λ

Given N1=2N2

T1T2=4



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