Moderate
A radioactive sample's activity drops from 640 Bq to 80 Bq in 12 hours. What is the half-life?
Correct answer: B. 4 hours
- A. 3 hours
- B. 4 hours
- C. 6 hours
- D. 8 hours
Explanation
Activity A = A0 × (1/2)(t/T1/2). Given 80/640 = 1/8 = (1/2)3, so 3 = 12/T1/2 , T1/2 = 12/3 = 4 hours.
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Atomic nuclei contain protons and neutrons, with nuclear size, mass defect and binding energy describing their stability. The work covers alpha, beta and gamma decay, decay equations, half-life and decay rate, along with radiation safety and medical applications such as imaging, radiotherapy and tracers.
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