Roentgen R
About the Roentgen
The roentgen measures exposure to X-rays and gamma rays by the ionisation they produce in air, exactly 2.58 × 10⁻⁴ coulombs per kilogram. It is named after Wilhelm Röntgen, who discovered X-rays in 1895. It has no SI special name and is now considered obsolete.
Related Units
Curie
Ci3.7 × 10¹⁰ Bq (exact)
The curie, exactly 3.7 × 10¹⁰ decays per second, was based on the activity of one gram of radium-226. It is named after...
Becquerel
Bq1 Bq = 1 s⁻¹ (one decay per second)
The becquerel is an activity of one radioactive decay per second, named after Henri Becquerel, who discovered...
Gray
Gy1 Gy = 1 J/kg = 1 m²·s⁻²
The gray measures absorbed dose of ionising radiation, one joule of energy deposited per kilogram of matter. It is...
Sievert
Sv1 Sv = 1 J/kg = 1 m²·s⁻²
The sievert measures the biological effect of radiation, weighting the absorbed dose by radiation type and tissue...