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Tritium has a half-life of \(12.5y\)  undergoing beta decay. What fraction of a sample of pure tritium will remain undecayed after \(25y\) .

Answer

As per the definition of half-life, half of the initial sample will remain un-decayed after \(12.5 y\). In the next \(12.5 y\), one-half of these nuclei would have been decayed. Thus, one fourth of the sample of the initial pure tritium will remain un-decayed.
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