Q. A radioactive substance contains 10000 nuclei and its half-life period is 20 days. The number of nuclei present at the end of 10 days is
A) 7070
B) 9000
C) 8000
D) 7500
Explanation
(a) We Know, $\frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{t/T}$
$\ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \ \frac{N}{10000} = \left( \frac{1}{2} \right)^{10/20}$
$\ \ N\ = \ \frac{10000}{\sqrt{2}}\ = \ \frac{10000}{1.414}\ = \ 7070$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.