Roentgen

Roentgen (R) is a unit of measurement for exposure to ionizing radiation (X-rays, gamma rays). Named after the German physicist Wilhelm Röntgen, who discovered X-rays in 1895, the roentgen measures the amount of ionization produced in air by X-ray or gamma radiation.

Definition

The roentgen is defined as the amount of radiation required to liberate positive and negative charges of one electrostatic unit of charge (esu) in one cubic centimeter of dry air at standard temperature and pressure (STP). This corresponds to the generation of approximately 2.08×10^9 ion pairs.

Usage

The roentgen is not a SI unit and is not commonly used in the scientific community worldwide. The SI unit for radiation exposure is the coulomb per kilogram (C/kg), which is approximately 3876 R. However, the roentgen is still used in some countries, including the United States, in certain applications in radiology, nuclear medicine, and radiation protection.

Conversion to other units

1 R = 2.58 × 10^-4 C/kg 1 R = 9.33 × 10^2 Gy in air 1 R = 0.877 rad in soft tissue

See also

• Sievert
• Becquerel
• Curie (unit)