Q. If half-life of a substance is 3.8 days and its quantity is $10.38\ g$. Then substance quantity remaining left after 19 days will be
A) $0.151\ g$
B) $0.32\ g$
C) $1.51\ g$
D) $0.16\ g$
Explanation
(b) Number of half lives $n = \frac{19}{3.8} = 5$; Now $\frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{n}$
$\Rightarrow \frac{N}{10.38} = \left( \frac{1}{2} \right)^{5} \Rightarrow N = 10.38 \times \left( \frac{1}{2} \right)^{5} = 0.32g$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.