Q. If half life of a radioactive element is $3\ hours$, after $9\ hours$ its activity becomes
A) 1/9
B) 1/27
C) 1/6
D) 1/8
Explanation
(d) By using $A = A_{0}\left( \frac{1}{2} \right)^{\frac{1}{T_{1/2}}} \Rightarrow \frac{A}{A_{0}} = \left( \frac{1}{2} \right)^{9/3} = \frac{1}{8}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.