Final answer:
The SI unit of exposure for radiation is the Roentgen (R). Other units like Gray (Gy) measure absorbed dose, and Sievert (Sv) account for biological effects of radiation on tissue, but for exposure, it is the Roentgen.
Step-by-step explanation:
The SI (International System of Units) unit of exposure for radiation is the Roentgen (Symbol: R). This unit measures the amount of radiation that produces an electrical charge of 2.58 × 10-4 C in 1 kg of dry air and is named after the German physicist Wilhelm Röntgen. However, when discussing the dose of radiation absorbed by biological tissue, the unit used is the Gray (Gy), where 1 Gy equals the absorption of one joule of radiation energy per kilogram of matter (J/kg).
Additionally, the Sievert (Sv) measures the biological effects of radiation absorbed, taking into account the energy and the biological effects of the type of radiation. The Röntgen equivalent for man (rem) is another unit for radiation damage frequently used in medicine, with the relationship that 1 Sv equals 100 rem. Despite the various units, for measuring exposure specifically, the Roentgen is the correct answer.