A certain radioactive mass decays from 64 gm to 2 gm in 20 days. What is its half - life?
Correct answer: B. 4 days
- A. 5 days
- B. 4 days
- C. 10 days
- D. 6 days
Explanation
Radioactive decay is an exponential decay process. Half life measures the time it takes for a given amount of the substance to become reduced by half as a consequence of decay; hence, half life is called half of decay.64-32-16-8-4-2 Half life=5Number of half lives= 20/5 = 4 days
This question appeared on the UHS MDCAT 2008 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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