Half-Life and Activity Quiz
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5 questions, one answer each
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1. What does the half-life of a radioactive isotope measure?
- A. A. The total time until all nuclei have decayed
- B. B. The time for the activity to halve
- C. C. The time for the mass to double
- D. D. The time for one nucleus to decay
2. A sample has an activity of 640 Bq. Its half-life is 5 minutes. What is its activity after 10 minutes?
- A. A. 320 Bq
- B. B. 160 Bq
- C. C. 80 Bq
- D. D. 640 Bq
3. Which statement about half-life is correct?
- A. A. It depends on how much of the sample is present
- B. B. It is the same regardless of sample size
- C. C. It decreases as the sample decays
- D. D. It can only be measured for alpha emitters
4. After 4 half-lives, what fraction of the original number of undecayed nuclei remains?
- A. A. 1/4
- B. B. 1/8
- C. C. 1/16
- D. D. 1/2
5. A radioactive isotope used to sterilise medical equipment must remain active for months in storage, while a hospital diagnostic tracer must clear from a patient's body within a day. Which combination of half-lives best matches these two uses?
- A. A. Sterilisation isotope: short half-life; tracer: long half-life
- B. B. Sterilisation isotope: long half-life; tracer: short half-life
- C. C. Both need the same half-life
- D. D. Half-life is irrelevant to either choice