WAEC Physics 2025 Objective — Question 36
Question 36 of 51 from the West African Examinations Council (WAEC) Physics 2025 Objective paper, with the correct answer and a full explanation.
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A hospital received 16g of a radioactive substance at 1300 hour GMT. At 1700 hour GMT, the fraction of the substance left undecayed was 1/16. Determine the half-life of the substance.
- A. 4 hours
- B. 3 hours
- C. 1 hourCorrect
- D. 0.5 hour
Explanation
Time elapsed = 1700-1300 = 4hrs. 1/16 = (1/2)ⁿ → n = 4 half-lives. T½ = t/n = 4/4 = 1 hour.
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