Q. Which of the following statement is not true for radioactive decay?
A) Decay constant increases with increase in temperature.
B) Amount of radioactive substance remained after three half lives is $\frac18$th of original amount.
C) Decay constant does not depend upon temperature.
D) Half life is $\ln2$ times of $\frac{1}{\text{rate constant}}$.
Explanation
[Solution by Dr. Abubacker] Radioactive decay is a nuclear process, so the decay constant is independent of temperature and statement (1) is not true. After 3 half-lives $\left(\frac12\right)^3=\frac18$ remains, and $t_{1/2}=\frac{\ln2}{\lambda}$. Answer (1).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.