The half-life of a radioactive substance is 30 min . The time (in minutes) taken between 40 % decay and 85 % decay of the same radioactive substance is

Step-by-step solution

Number of active nuclei falls from 60% to 15% So the sample becomes 1 4 t h = 1 2 2 t h So the number of half-lives = 2 Time t = 2 × 30 = 60   min