## Formula

1 R (roentgen) exposure is approximately equivalent to 10 mSv tissue dose

Radiation exposure refers to the measure of the ionization that is produced in air by X-=rays or gamma rays. The SI unit of radiation exposure is roentgen. The X-rays and gamma rays are expressed in the units of roentgen (R). The exposure usually occurs as the result of an accidental spill of radioactive material. The common units of radiation exposure are roentgen, sievert, rem, rep, parker, coulomb per kilogram, millicoulomb per kilogram.

Radiation exposure is the sum of the electric charges on all ions of one sign that are produced when all electrons liberated by photons in a volume of air are stopped completely and divided by the mass of air in the volume element. An exposure of the whole human body to approximately 10,000 rad (100 gray) causes neurologic and cardiovascular breakdown and is fatal within 24 hours.

Example:
Convert the 25 roentgen to various other units of radiation exposure.

Solution:
coulomb/kilogram [C/kg] = 0.006449999999999999
millicoulomb/kilogram [mC/kg] = 6.45
microcoulomb/kilogram = 6450
tissue roentgen = 25
parker = 25
rep = 25