Q. 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) $A_{1}t_{1} - A_{2}t_{2}$
B) $A_{1} - A_{2}$
C) $(A_{1} - A_{2})/\lambda$
D) $\lambda(A_{1} - A_{2})$
Explanation
(c) $A_{1} = \lambda N_{1}$
$A_{2} = \lambda N_{2}$
$N_{1} - N_{2} = \left\lbrack \frac{A_{1} - A_{2}}{\lambda} \right\rbrack$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.