Four different radioactive isotopes are prepared such that their samples all initially emit radiation at the same rate. As time passes, the rate of emission decreases for each of the samples.
The half-lives of the four isotopes are shown in the table below:
| Isotope | Half-life |
|---|---|
| Xenon-135 | 9.1 hours9.1\text{ hours}9.1 hours |
| Sodium-24 | 15 hours15\text{ hours}15 hours |
| Gold-198 | 2.7 days2.7\text{ days}2.7 days |
| Cobalt-60 | 5.3 years5.3\text{ years}5.3 years |
Which sample of isotope has the greatest decrease in its rate of emission?
Xenon-135
Sodium-24
Gold-198
Cobalt-60
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.