Q. The half-life of radioactive Polonium $(Po)$ is $138.6\ days$. For ten lakh Polonium atoms, the number of disintegration in 24 hours is
A) 2000
B) 3000
C) 4000
D) 5000
Explanation
(d) $n = \frac{24}{24 \times 138.6} = \frac{1}{138.6};$ Now $\frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{n} = \left( \frac{1}{2} \right)^{1/138.6}$
$\Rightarrow N = 10,00000\left( \frac{1}{2} \right)^{1/138.6} = 995011$
So number of disintegration
$= 1000000 - 995011 = 4989 = 5000$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.