Definition: | the quotient of dQ by dm, where dQ is the total electric charge of the ions of one sign produced in air when all electrons (negative and positive), liberated by photons in air of mass dm are completely stopped in air
NOTE – The SI unit of exposure is the coulomb per kilogram (C kg−1). The earlier special unit of exposure, still in temporary use, was the roentgen.
1 R = 2,58 × 10−4 C kg−1
|