A radiation detector is set near to a radioactive source. The detector does not enclose the source. Radiation is emitted in all directions and, because of this, the activity of the source and the measured count rate are not the same. Suggest two other reasons why the activity and the measured count rate may differ.
The graph in Fig. 12.1 shows how the measured count rate in (a) changes with time $t$. State which feature of Fig. 12.1 reveals the random nature of radioactive decay.
Use Fig. 12.1 to work out the half-life of the radioactive isotope in the source.
The readings in (b) were obtained at room temperature. A second sample of this isotope is heated to a temperature of $500\,^\circ\text{C}$. 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 determined. State, with a reason, the difference, if any, in 1. the half-life, 2. the measured count rate at any given time.