Question

What will happen in a time of 7 hours, if a radioactive substance has an average life of 7 hours?

(a) Half of the active nuclei decay

(b) Less half of the active nuclei decay

(c) More than half of the active nuclei decay

(d) All active nuclei decay

This question was addressed to me in homework.

The origin of the question is Nucleus in portion Nucleus of Physics – Class 12

Answer 1

Correct option is (c) More than half of the active nuclei decay

The best I can explain: In one average life, i.e. at 7 hours, 63.2 % of the active nuclei will decay. Therefore, in a time of 7 hours, it can be considered that more than half of the active nuclei will decay.