Q. If $N_{0}$ is the original mass of the substance of half life period $T_{1/2} = 5\ years$, then the amount of substance left after $15\ years$ is
A) $N_{0}/8$
B) $N_{0}/16$
C) $N_{0}/2$
D) $N_{0}/4$
Explanation
(a) $N = N_{0}\left( \frac{1}{2} \right)^{\frac{t}{T_{1/2}}} = N_{0}\left( \frac{1}{2} \right)^{\frac{15}{5}} = \frac{N_{0}}{8}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.