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13.Nuclei
easy
The decay constant of a radio isotope is $\lambda$. If $A_1$ and $A_2$ are its activities at times $t_1$ and $t_2$ respectively, the number of nuclei which have decayed during the time $(t_1 - t_2)$
A
$A_1t_1-A_2t_2$
B
$A_1-A_2$
C
$(A_1-A_2)/λ$
D
$λ (A_1-A_2)$
(AIPMT-2010)
Solution
$A_{1}=\lambda N_{1}$ at time $t_1$
$A_{2}=\lambda N_{2}$ at time $t_2$
Therefore, number of nuclei decayed during time interval $\left(t_{1}\,-\,t_{2}\right)$ is
$N_{1}-N_{2}=\frac{\left[A_{1}-A_{2}\right]}{\lambda}$
Standard 12
Physics
