Which type of detector involves tracking changes in electrical signals caused by radon decay?

The correct choice involves a continuous radon monitor, which is designed to measure radon levels in the air by continuously tracking changes in electrical signals resulting from radon decay. This type of detector works by using a sensor that responds to the ionization caused by alpha particles emitted from radon and its decay products. When radon decays, it releases alpha particles, which interact with the monitor’s sensor. These interactions produce electrical signals that can be monitored in real-time, providing a continuous measurement of radon concentration.

In contrast, other types of detectors listed each have different operational mechanisms. For instance, an alpha track detector uses a solid-state film that captures tracks left by alpha particles from radon decay over a longer exposure period, while a liquid scintillation device detects scintillation light produced from radioactive decay in a liquid sample. Solid state detectors typically rely on semiconductor materials and have distinct detection principles that do not involve continuous electrical signal changes in the same way a continuous radon monitor does.

Therefore, the continuous radon monitor's unique ability to keep track of varying radon concentrations through electrical signal changes is what makes it particularly effective for real-time monitoring of environmental radon levels.