A sample of a radioactive isotope emits 8000 β\betaβ-particles per second.
After 45 minutes, the rate of emission has fallen to 250 β\betaβ-particles per second.
What is the half-life of this isotope?
3.0 minutes3.0\text{ minutes}3.0 minutes
9.0 minutes9.0\text{ minutes}9.0 minutes
15 minutes15\text{ minutes}15 minutes
22.5 minutes22.5\text{ minutes}22.5 minutes
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.