The radioactivity of a certain radioactive element drops to 1/64 of its initial value in 30 seconds. Its half-life is:
Correct answer: B. 5 seconds
- A. 2 seconds
- B. 5 seconds
- C. 4 seconds
- D. 6 seconds
Explanation
Radioactivity drops to = 1 / 64 of original value Number of half lives = n (1 / 2)n = 1 / 64 (1 / 2)6 = 1 / 64 n = 6 Total time = 30 seconds t1/2 = 30 / n t1/2 = 30 / 6 = 5 seconds
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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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