An accidental spill of the radioisotope tritium, 13H^3_1\text{H}13H, occurs in a research laboratory. After 49.2 years49.2\text{ years}49.2 years have passed, the quantity of tritium present is 25.0% of its original level in some areas, but in others, the standard calculations are needed. For this spill, after 49.2 years49.2\text{ years}49.2 years, the overall average level of tritium present is 6.25% of its original level.
What is the half-life of tritium?
9.8 years9.8\text{ years}9.8 years
12.3 years12.3\text{ years}12.3 years
16.4 years16.4\text{ years}16.4 years
24.6 years24.6\text{ years}24.6 years
484 exam-style questions on CIE IGCSE Physics 5.2 Radioactivity, covering 5.2.1 Background radiation and measuring count rate, 5.2.2a Alpha, beta and gamma emission, 5.2.2b Deflection and ionising effects of nuclear radiation, 5.2.3a Radioactive decay, 5.2.3b Effects of decay on the nucleus and decay equations, 5.2.4a Half-life, 5.2.4b Choosing isotopes for applications, and 5.2.5 Effects of ionising radiation and safety precautions. Each one has a worked solution and a mark scheme showing where the marks go.