The half-life of 131I is 8 days. Given a sample of 131I at time t = 0,...
The result follows from the formula based on laws of radioactive decay N = N0e–λt The nucleus start decaying after time t = 0
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The half-life of 131I is 8 days. Given a sample of 131I at time t = 0,...
Explanation:
The half-life of a radioactive substance is the time it takes for half of the nuclei in a sample to decay. In the case of 131I, the half-life is 8 days. This means that after 8 days, half of the 131I nuclei in the sample will have decayed, and after another 8 days, half of the remaining nuclei will have decayed, and so on.
Option A: No nucleus will decay before t = 4 days.
- This statement is incorrect because the half-life of 131I is 8 days, so it is possible for some nuclei to decay before 4 days.
Option B: No nucleus will decay before t = 8 days.
- This statement is incorrect because the half-life of 131I is 8 days, and after 8 days, half of the nuclei will have decayed.
Option C: All nuclei will decay before t = 16 days.
- This statement is incorrect because the half-life of 131I is 8 days, and it will take multiple half-lives for all the nuclei to decay. After 16 days, only three half-lives have passed, so there will still be some nuclei remaining.
Option D: A given nucleus may decay at any time after t = 0.
- This statement is correct because radioactive decay is a random process. While the half-life gives an average time for decay, any given nucleus may decay at any time after t = 0. Some nuclei may decay early, while others may decay later.
Thus, option D is the correct answer as it correctly describes the nature of radioactive decay and the behavior of individual nuclei in a sample of 131I.