A 32g radioactive elements decays and remains 2g after 60 days. What is half-life of this radioactive elements?
Correct answer: D. 15 days
- A. 2 days
- B. 6 days
- C. 10 days
- D. 15 days
Explanation
The half-life of a radioactive element is the time it takes for half of the initial quantity to decay. In this case, the element started with 32g and remains 2g after 60 days. To find the half-life, we can calculate how many times the initial quantity must halve to reach 2g: 32g → 16g (halved once) → 8g (halved twice) → 4g (halved three times) → 2g (halved four times) So, the element halved four times to reach 2g. Since this took 60 days, the half-life is: 60 days / 4 = 15 days
This question appeared on the NUMS 2023 paper, which you can sit online with every answer explained.
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About Half-life and Rate of Decay
Half-life is the time required for half the unstable nuclei in a sample to decay, and it remains constant for a particular radioactive nuclide. Questions use the exponential decay law, decay constant, activity, remaining quantity and mean life. Radioactive decay is random for individual nuclei but predictable for large samples.
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