Question detail
If a radioactive substance has a half-life of 5 years, how long will it take for the substance to decay to one-eighth of its original amount?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
MCQ
Type
practice
Style
Topic
Atoms and nuclear radiation
Question
- A. 5 years
- B. 10 years
- C. 15 years
- D. 20 years
Answer
15 years
Explanation
It takes three half-lives (5 years each) to reduce to one-eighth of the original amount, which is 15 years.
Common mistake
Misunderstanding Half-Life Definition
Students often confuse half-life with the time taken for the entire sample to decay, rather than the time for half of the radioactive nuclei to decay.
Emphasize that half-life specifically refers to the time it takes for half of the radioactive nuclei in a sample to decay, not the entire sample.
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