An isotope of iodine has a half-life of 20 h.
The table gives data from an experiment to show how the rate of decay of the isotope varies with time.
The background count rate has not been subtracted from these data.
Time / h010203040Count rate / counts/s510370270200150 \begin{array}{|c|c|c|c|c|c|}\hline\text{Time } / \text{ h} & 0 & 10 & 20 & 30 & 40 \\\hline\text{Count rate } / \text{ counts/s} & 510 & 370 & 270 & 200 & 150 \\\hline\end{array} Time / hCount rate / counts/s051010370202703020040150What is the background radiation count rate?
15 counts/s15\text{ counts/s}15 counts/s
20 counts/s20\text{ counts/s}20 counts/s
30 counts/s30\text{ counts/s}30 counts/s
45 counts/s45\text{ counts/s}45 counts/s
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.