Radioactive decay and half-life Quiz
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5 questions, one answer each
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1. An isotope has a half-life of 5.0 years. What is its decay constant?
- A. 0.14 years⁻¹
- B. 0.20 years⁻¹
- C. 3.5 years⁻¹
- D. 5.0 years⁻¹
2. A sample has an activity of 800 Bq. What is its activity after three half-lives?
- A. 400 Bq
- B. 267 Bq
- C. 0 Bq
- D. 100 Bq
3. A graph of ln A against t for a radioactive sample is a straight line. What does the gradient equal?
- A. λ
- B. −λ
- C. t½
- D. ln 2
4. A sample contains 2.0 × 10¹⁰ undecayed nuclei, and λ = 3.0 × 10⁻⁵ s⁻¹. What is its activity?
- A. 6.7 × 10¹⁴ Bq
- B. 1.5 × 10⁻¹⁵ Bq
- C. 6.0 × 10⁵ Bq
- D. 2.0 × 10¹⁰ Bq
5. For a source with λ = 0.020 s⁻¹, what fraction of the original activity remains after 50 s?
- A. 0.63
- B. 0.50
- C. 0.02
- D. 0.37