What is the unit of measurement for radiation exposure?

The unit of measurement for radiation exposure is indeed the Gray (Gy) or the roentgen (R). The Gray is a unit that quantifies the amount of ionizing radiation that gets absorbed by a material or tissue. Specifically, one Gray is defined as the absorption of one joule of radiation energy per kilogram of matter.

The roentgen, on the other hand, is traditionally used to measure exposure to X-rays and gamma rays in air. It represents the amount of ionization produced in air by X-rays or gamma rays and is a useful measure in the context of radiation safety and monitoring.

Joules (J) are a unit of energy and do not directly measure exposure, while volts (V) measure electric potential, and watts (W) measure power, which is the rate of energy transfer. These other units do not apply directly to the measurement of radiation exposure in the context of ionizing radiation. Thus, Gray and roentgen are the appropriate units for understanding radiation exposure and its effects on biological tissue or the environment.