Q. A sample contains $16\ g$ of a radioactive material, the half life of which is two days. After 32 days, the amount of radioactive material left in the sample is
A) Less than $1\ mg$
B) $\frac{1}{4}g$
C) $\frac{1}{2}g$
D) $1g$
Explanation
(a) Remaining amount
$= 16 \times \left( \frac{1}{2} \right)^{32/2} = 16 \times \left( \frac{1}{2} \right)^{16} = \left( \frac{1}{2} \right)^{12} < 1mg$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.