Q. What fraction of a radioactive material will get disintegrated in a period of two half-lives
A) Whole
B) Half
C) One-fourth
D) Three-fourth
Explanation
(d) $\frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{n},n = 2 \Rightarrow \frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{2} = \frac{1}{4}$
So disintegrated part $= 1 - \frac{N}{N_{0}} = 1 - \frac{1}{4} = \frac{3}{4}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.