Radioactive decay is described as being both random and spontaneous.
Which row in the table correctly identifies an experimental observation that demonstrates each of these two characteristics?
Observation demonstrating random nature: The decay rate of a sample of 14C^{14}\text{C}14C is unaffected when it is chemically reacted to form carbon dioxide (CO2\text{CO}_2CO2). | Observation demonstrating spontaneous nature: The measured count rate of a long-lived radioactive source fluctuates over short time intervals.
Observation demonstrating random nature: The measured count rate of a long-lived radioactive source fluctuates over short time intervals. | Observation demonstrating spontaneous nature: The decay rate of a sample of 14C^{14}\text{C}14C is unaffected when it is chemically reacted to form carbon dioxide (CO2\text{CO}_2CO2).
Observation demonstrating random nature: The activity of a sample of an isotope decreases exponentially over time. | Observation demonstrating spontaneous nature: The kinetic energy of the emitted α\alphaα particles is discrete for a given nuclide.
Observation demonstrating random nature: The kinetic energy of the emitted α\alphaα particles is discrete for a given nuclide. | Observation demonstrating spontaneous nature: The activity of a sample of an isotope decreases exponentially over time.
128 exam-style questions on AQA A Level Physics Radioactivity (A-level only), covering Rutherford scattering (A-level only), $\alpha$ , $\beta$ and $\gamma$ radiation (A-level only), Radioactive decay (A-level only), Nuclear instability (A-level only), Nuclear radius (A-level only), Mass and energy (A-level only), Induced fission (A-level only), and Safety aspects (A-level only). Each one has a worked solution and a mark scheme showing where the marks go.