Q. The half-life of a radioactive substance is 30 minutes. The time (in minutes) taken between 40% decay and 85% decay of the same radioactive substance is :-
A) 15
B) 30
C) 45
D) 60
Explanation
[Solution] Remaining goes from 60% to 15%, a factor of 4 = two half-lives = 60 min. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.