The Roentgen (R) unit is used to measure which type of exposure?

The Roentgen (R) unit is used to measure which type of exposure?

• A. Electrical resistance
• B. Ionizing radiation exposure
• C. Thermal energy
• D. Magnetic fields

Answer: (B)

The Roentgen measures exposure to ionizing radiation—the amount of ionization produced in a unit mass of air by X-rays or gamma rays. It quantifies how much radiation is present in the air, not how much energy is absorbed by a material. That’s why it’s tied to ionizing radiation rather than electrical resistance, thermal energy, or magnetic fields. In modern practice, exposure is expressed in coulombs per kilogram, while absorbed dose and dose equivalent use other units (gray and sievert).

The Roentgen measures exposure to ionizing radiation—the amount of ionization produced in a unit mass of air by X-rays or gamma rays. It quantifies how much radiation is present in the air, not how much energy is absorbed by a material. That’s why it’s tied to ionizing radiation rather than electrical resistance, thermal energy, or magnetic fields. In modern practice, exposure is expressed in coulombs per kilogram, while absorbed dose and dose equivalent use other units (gray and sievert).