Units of Exposure and Absorbed Dose

Protection of individuals against radiation necessitates the completion of two tasks  

Construction of instruments that measure the intensity of radiation 

Neither of these tasks can be accomplished without the means of quantitative description of radiation, i.e., without defining radiation units. 

The radiation effect is measured in terms of exposure or dose. Exposure is defined as charge released per unit mass of air. Dose is defined as energy absorbed per unit mass of material. The first radiation unit to be defined was 

1 R = exposure due to X-rays or gamma-rays of such intensity that the electrons produced by this radiation in 1 cm of dry air, at standard temperature and pressure, generate along their tracks electron-ion pairs carrying a total charge of 1 esu of either sign 

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