This topic will cover the basics of radiation, including the definition, types of radiation (ionizing and non-ionizing), sources of radiation, and units of measurement.
Introduction to Radiation
Key concepts, types, sources, interactions, and safety considerations
| Definition | Explanation |
|---|---|
| Radiation | The emission and propagation of energy in the form of particles or electromagnetic waves through space or a material medium. |
| Ionizing vs. Non‑ionizing | Ionizing radiation carries enough energy to remove tightly bound electrons from atoms, creating ions. Non‑ionizing radiation lacks this energy; it can excite atoms but not ionize them. |
| Category | Sub‑type | Typical Energy Range | Primary Examples |
|---|---|---|---|
| Electromagnetic | Gamma (γ) | > 100 keV (up to several MeV) | Nuclear decay, astrophysical sources |
| X‑ray | 0.1 keV – 100 keV | Medical imaging, industrial inspection | |
| Ultraviolet (UV) | 3 eV – 100 eV | Sunlight, UV lamps | |
| Visible light | 1.65 eV – 3.1 eV | Sun, LEDs | |
| Infrared (IR) | 0.001 eV – 1.65 eV | Thermal cameras, heaters | |
| Particle | Alpha (α) | 4–9 MeV (He²⁺) | Decay of heavy nuclei (U‑238, Pu‑239) |
| Beta (β) | 0.01–3 MeV (e⁻ or e⁺) | Decay of C‑14, Sr‑90 | |
| Neutron | 0.025 eV – several MeV | Nuclear reactors, spallation sources | |
| Proton, heavy ions | > MeV per nucleon | Particle accelerators, cosmic rays | |
| Acoustic / Mechanical | Sound waves | 10⁻⁹ eV – 10⁻² eV | Ultrasound imaging, sonar |
Only the first three rows (γ, X‑ray, α, β, neutrons) are typically classified as ionizing radiation.
| Source | Natural | Man‑made |
|---|---|---|
| Cosmic rays | High‑energy particles from space | None |
| Terrestrial radionuclides | Uranium, thorium, radon in rocks/soil | None |
| Radon gas | Decay product of uranium in the ground | None |
| Medical | Diagnostic X‑rays, CT scans, radiotherapy | Radiopharmaceuticals |
| Industrial | Radiography, gauge devices, smoke detectors | Industrial irradiators |
| Nuclear power | Fission product emissions (controlled) | Reactor operations, spent fuel |
| Research | Particle accelerators, neutron sources | Synchrotrons, cyclotrons |
| Interaction | Dominant Energy Range | Effect on Matter |
|---|---|---|
| Photoelectric effect | ≤ 100 keV | Photon absorbed, electron ejected |
| Compton scattering | ~100 keV – 10 MeV | Photon loses part of its energy, changes direction |
| Pair production | > 1.022 MeV | Photon creates e⁻/e⁺ pair near nucleus |
| Rayleigh scattering | < 10 |