Question detail
If a radioactive substance has a half-life of 5 years, how many years will it take for the activity to reduce from 160 Bq to 20 Bq?
Try the question, check the answer, then read the explanation to understand the curriculum point.
At a glance
Question
Type
exam_style
Style
Topic
Atoms and nuclear radiation
Question
If a radioactive substance has a half-life of 5 years, how many years will it take for the activity to reduce from 160 Bq to 20 Bq?
Answer
15 years
Explanation
This question assesses the ability to calculate the number of half-lives based on changes in activity. The activity reduces from 160 Bq to 20 Bq, which requires three half-lives.
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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