What unit is used to express exposure in radiation measurement?

The unit used to express exposure in radiation measurement is the coulomb per kilogram (C/kg), which quantifies the amount of ionization produced in air by x-rays or gamma rays. This measurement is directly related to the exposure of radiation and is used to characterize how much radiation energy is being absorbed by the air.

C/kg provides a clear indication of the quantity of ion pairs created in a given mass of air, which is critical in radiation safety and protection practices. It is specifically designed for measuring exposure in terms of ionizing radiation in the air, making it particularly relevant for radiological evaluations.

Understanding this unit is essential for professionals in the field of radiology, as it helps gauge the potential risk associated with exposure to ionizing radiation and aids in developing appropriate protective measures. The other options, while related to radiation and dosimetry, refer to different concepts or units such as dose and biological effect rather than direct exposure measurement.