question_answer

Tritium has a half-life of 12.5 years against beta decay. What fraction of a sample of pure tritium will remain undecayed after 25 years?                         

Answer:

                From the definition of half-life, we can say that (i) \[\frac{1}{2}\] of the initial tritium nuclei remain undecayed after the first 12.5 years, (ii) \[\frac{1}{2}\] of the remaining nuclei will decay in the next 12.5 years, and hence (iii) \[\frac{1}{2}\] of the initial tritium nuclei will remain undecayed after 25 years.