Q. The ratio of molecular mass of two radioactive substances is 3/2 and the ratio of their decay constants is 4/3. Then, the ratio of their initial activity per mole will be

A) $2$
B) $4/3$
C) $\frac{8}{9}$
D) $9/8$
Explanation

(b) Activity, $A = \frac{- N}{dt} = \lambda N$
As the number of nuclei $(N)$ per mole are equal for both the substances, irrespective of their molecular mass, therefore, $A \propto \lambda$
$\frac{A_{1}}{A_{2}} = \frac{\lambda_{1}}{\lambda_{2}} = \frac{4}{3}$

Dr. Abubacker
Reviewed by Dr. Abubacker

Physics Educator & NEET/JEE Specialist

Ph.D. in Physics with 19+ years of teaching experience.

Want more practice?
Practice Nuclei MCQs