Q. A radioactive material has an initial amount $16g$. After $120\ days$ it reduces to $1g$, then the half-life of radioactive material is
A) $60\ days$
B) $30\ days$
C) $40\ days$
D) $240\ days$
Explanation
(b) $\frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{t/T_{1/2}} \Rightarrow \left( \frac{1}{16} \right) = \left( \frac{1}{2} \right)^{120/T_{1/2}}$
$\left( \frac{1}{2} \right)^{4} = \left( \frac{1}{2} \right)^{120/T_{1/2}} \Rightarrow 4 = \frac{120}{T_{1/2}} \Rightarrow T_{1/2} = 30$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.