Q. The half-life of a radioactive substance is 40 years. How long will it take to reduce to one fourth of its original amount and what is the value of decay constant
A) 40 year, 0.9173/year
B) 90 year, 9.017/year
C) 80 year, 0.0173/year
D) None of these
Explanation
(c) To nucleus one fourth it takes time $t = 2\left( T_{1/2} \right) = 2 \times 40 = 80\ years$
Decay constant $\lambda = \frac{0.693}{T_{1/2}} = \frac{0.693}{40} = 0.0173years$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.