A radiation detector is placed near a radioactive source, but it does not enclose the source. Since radiation leaves the source in all directions, the source activity and the measured count rate are not the same. Suggest two further reasons why these two quantities may differ.
The way the measured count rate in (a) changes with time $t$ is plotted in Fig. 12.1. State the feature of Fig. 12.1 that shows radioactive decay is random.
Use Fig. 12.1 to find the half-life of the radioactive isotope in the source.
The measurements in (b) were made at room temperature. A second sample of this isotope is then heated to $500\,^{\circ}\text{C}$. The initial count rate at time $t = 0$ is the same as in (b). The variation with time $t$ of the measured count rate from the heated source is then found. State, with a reason, what change, if any, occurs in (1) the half-life, and (2) the measured count rate at any particular time.