Q. The half life period of radium is $1600\ years$. The fraction of a sample of radium that would remain after $6400\ years$ is
A) $1/4$
B) $1/2$
C) $1/8$
D) $1/16$
Explanation
(d) Fraction $= \frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{\frac{6400}{1600}} = \left( \frac{1}{2} \right)^{4} = \frac{1}{16}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.