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RAD

Definition

The unit of absorbed dose of radiation. The absorbed dose is one rad when one kg absorbs 102 joules of energy. In 1956 the rad replaced the roentgen (unit of radiation exposure) for clinical work involving X-rays or radioactive sources. In practice the rad and the roentgen both represent about the same amount of energy since 1,000 rads equal 1100 ± 50 roentgen but unlike the roentgen the rad is applicable to all types of radiation.

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