Radiation Dose
A measure of the energy deposited in matter by ionising radiation.
Formula / equation
D = E / m
Unit
Gy
In depth
Absorbed dose in grays measures deposited energy alone, while equivalent dose in sieverts weights it by how damaging the radiation type is, and effective dose weights further by the sensitivity of the tissue exposed. Only the last is meaningful for assessing overall risk.
Examples in the real world
A chest X-ray delivers about 0.1 mSv; the average annual background dose is roughly 2.4 mSv.