IIT-JEE 2008 · Paper 2 · Physics Q24

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PhysicsSingle correct+3 / -1Question 24 of 66

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

20 years and 5 years, respectively

20 years and 10 years, respectively

10 years each

5 years each

Answer and worked solution

Official answer: A

Activity $A=\lambda N$ . With $N_1=2N_2$ :
$\frac{A_1}{A_2}=\frac{\lambda_1\cdot2N_2}{\lambda_2N_2}=\frac5{10}\implies\frac{\lambda_1}{\lambda_2}=\frac14.$
So $T_1=4T_2$ : 20 years and 5 years fits.

(A)

Topics:Radioactive decay

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IIT-JEE 2008 · Paper 2, Physics question 24