Q. A sample of an element is 10.38 g. If half-life of element is 3.8 days, then after 19 days, how much quantity of element remains?
A) 0.151 g
B) 0.32 g
C) 1.51 g
D) 0.16 g
Explanation
(b) $\frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{t/T} = \frac{m}{m_{0}}\left( \frac{1}{2} \right)^{19/3.8} = \frac{m}{10.38}$
$\left( \frac{1}{2} \right)^{19/3.8} = \frac{m}{10.38}$
$m = 10.38 \times \left( \frac{1}{2} \right)^{5} = \frac{10.38}{32} = 0.32\ g$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.