in one cubic centimeter of dry air. 1 roentgen = . However, the effect of ionizing radiation on matter (especially living tissue) is more closely related to the amount of energy deposited into them rather than the charge generated. This measure of energy absorbed is called the absorbed dose: The gray (Gy), which has units of (joules/kilogram), is the SI unit of absorbed dose, and it is the amount of radiation required to deposit one joule of energy in one kilogram of any kind of matter. The rad is the (obsolete) corresponding traditional unit, equal to 10 millijoules of energy deposited per kilogram. 100 rad = 1 gray. The equivalent dose is the measure of the biological effect of radiation on human tissue. For X-rays it is equal to the absorbed dose. The Roentgen equivalent man (rem) is the traditional unit of equivalent dose. For X-rays it is equal to the rad, or, in other words, 10 millijoules of energy deposited per kilogram. 100 rem = 1 Sv. The sievert (Sv) is the SI unit of equivalent dose, and also of effective dose. For X-rays the "equivalent dose" is numerically equal to a Gray (Gy). 1 Sv = 1 Gy. For the "effective dose" of X-rays, it is usually not equal to the Gray (Gy). See also Backscatter X-ray Detective quantum efficiency High-energy X-rays Macintyre's X-Ray Film – 1896 documentary radiography film N ray Neutron radiation NuSTAR Radiographer Reflection (physics) Resonant inelastic X-ray scattering (RIXS) Small-angle X-ray scattering (SAXS) The X-Rays – 1897 British short silent comedy film X-ray absorption spectroscopy X-ray marker X-ray nanoprobe X-ray reflectivity X-ray vision X-ray welding References External links Röntgen's discovery of X-rays (PDF; English translation) Oakley, P. A., Navid Ehsani, N., & Harrison, D. E. (2020). 5 Reasons Why Scoliosis X-Rays Are Not Harmful. Dose-Response. https://doi.org/10.1177/1559325820957797 Electromagnetic spectrum IARC Group 1 carcinogens Ionizing radiation Medical physics Radiography Wilhelm Röntgen 1895 in science 1895 in Germany