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NEET 2011 (AIPMT, Prelims) · Law of Radioactive Decay

Law of Radioactive Decay question from NEET 2011 (AIPMT, Prelims)

Q101NEET 2011 · AIPMT · PRELIMSEasy

Law of Radioactive Decay

The half life of a radioactive isotope X is 50 years. It decays to another element Y which is stable. The two elements X and Y were found to be in the ratio of 1: 15 in a sample of a given rock. The age of the rock was estimated to be

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Answer: (b)

$N_0 = N_X + N_Y$ , so $\frac{N_X}{N_0} = \frac{1}{1+15} = \frac{1}{16} = \left(\frac{1}{2}\right)^4$ .
Age $= 4\times50 = 200$ years.
So the answer is (b) 200 years.

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