Orders of magnitude (radiation) Orders of magnitude (radiation) Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning. Although the International System of Units (SI) defines the sievert (Sv) as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1000 of a rem and 1 rem equals 0.01 Sv. Light radiation sickness begins at about 50–100 rad (0.5–1 gray (Gy), 0.5–1 Sv, 50–100 rem, 50,000–100,000 mrem). The following table includes some dosages for comparison purposes, using millisieverts (mSv) (one thousandth of
Ionizing radiation through the photoelectric effect and the Compton effect. Either of those interactions will cause the ejection of an electron from an atom at relativistic speeds, turning that electron into a beta particle (secondary beta particle) that will ionize many other atoms. Since most of the affected atoms are ionized directly by the secondary beta particles, photons are called indirectly ionizing radiation. Photon radiation is called gamma rays if produced by a nuclear reaction, subatomic particle decay, or radioactive decay within the nucleus. It is otherwise called x-rays if produced outside the nucleus. The generic term photon is therefore used to