Rad (CGS unit)

Last revised by Andrew Murphy on 29 Mar 2020

The rad (symbol rad) is a legacy unit in the cgs system for the absorbed dose of ionizing radiation, although it remains in widespread use in the United States. 

The rad is defined as the dose represented by 100 ergs of energy being absorbed by one gramme of matter. The erg is the unit of energy in the cgs system, where one erg = 1 x 10-7 joules. Practically-speaking, especially for the contemporary user, one rad = 0.01 Gy = 0.01 Jkg-1 or alternatively one gray = 100 rads.

History and etymology

Rad is an abbreviation of radiation absorbed dose. 

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