Which of the following is used to measure ionizing radiation exposure?

The correct answer is the dosimeter, which is a device specifically designed to measure an individual’s exposure to ionizing radiation over time. It typically contains materials that react to radiation exposure, allowing for the quantification of cumulative dose absorbed by the wearer. This makes dosimeters essential for monitoring exposure in occupational settings and ensuring that it remains within safe limits.

While other devices listed have specific uses in radiation detection, they do not serve the same purpose as dosimeters. A thermometer, for example, measures temperature, which is unrelated to ionizing radiation. The Geiger-Muller counter is a type of radiation detection instrument that can indicate the presence and intensity of ionizing radiation but does not measure personal exposure over time like a dosimeter does. Similarly, a radon detector is specialized for measuring radon gas levels and is not designed to provide a cumulative dose from various sources of ionizing radiation.