Q. Half-life of radio-active substance is 140 days. Initially, is 16 g. Calculate the time for this substance when it reduces to 1 g
A) 140 days
B) 280 days
C) 420 days
D) 560 days
Explanation
(d) $\frac{N}{N_{0}} = \left( \frac{1}{2} \right)^{n} = \frac{1}{16};n = 4$
$\therefore t = 4 \times 140 = 560$ days
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.