History

'Gray' History

Gray (Gy) is the derived SI unit for absorbed dose, specific energy and kerma (kinetic energy in matter). This unit was named after the English physicist and radiologist Louis Harold Gray. 1 Gray is the dose of energy absorbed by a homogeneously distributed material with a mass of 1 kilogram when exposed to ionising radiation bearing 1 joule of energy. 1 Gy = 1 J/kg