The rad is a largely obsolete unit of absorbed radiation dose, with symbol rad. Radiation, as in Physics, is Energy in the form of waves or moving Subatomic particles emitted by an atom or other body as it changes from a higher energy The rad was first proposed in 1918 as "that quantity of X rays which when absorbed will cause the destruction of the [malignant mammalian] cells in question. . . "^[1] It was defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter. An erg is the unit of Energy and Mechanical work in the centimetre-gram-second (CGS system of units symbol "erg" For other uses of the words gram or gramme see Gram (disambiguation. It was restated in SI units in 1970 as the dose causing 0. 01 joule of energy to be absorbed per kilogram of matter. The joule (written in lower case ˈdʒuːl or /ˈdʒaʊl/ (symbol J) is the SI unit of Energy measuring heat, Electricity In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός

It is now superseded in the SI by the gray; 100 rad are equal to 1 gray. The gray (symbol Gy is the SI unit of absorbed radiation dose. The continued use of the rad is "strongly discouraged" by the National Institute of Standards and Technology. ^[2]

See also

• Röntgen
• Röntgen equivalent man
• sievert
• gray

References