Question detail
A radioactive substance has an initial activity of 160 Bq. After 3 half-lives, what will be the remaining activity?
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. 20 Bq
- B. 40 Bq
- C. 80 Bq
- D. 10 Bq
Answer
20 Bq
Explanation
20 Bq is correct because the worked solution uses remaining = initial / 2^n and substitutes the values from the question. This keeps activity, count rate, atomic number, mass number and neutron count distinct for Atomic structure.
Common mistake
Counting Half-Lives Mistake
Students often miscalculate the number of half-lives that have passed by not correctly halving the initial count rate multiple times.
To fix this, students should clearly outline the initial count rate and systematically halve it for each half-life until they reach the final count rate, ensuring they count the number of halvings accurately.
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