radiation

Radiation is energy that propagates through space or matter as particles or waves. It encompasses electromagnetic radiation—photons such as visible light, infrared, ultraviolet, X-rays, and gamma rays—and particle radiation such as alpha and beta particles and neutrons. A key distinction is ionizing radiation, which has enough energy to remove electrons from atoms, and non-ionizing radiation, which generally does not.

Natural sources include cosmic rays from space, terrestrial radionuclides such as uranium and radon, and internal exposure from ingested radionuclides. Human-made sources include medical imaging (X-ray and CT), nuclear power and weapons, industrial gauges, and consumer devices. Radiation exposure is quantified with several measures: activity in becquerels (disintegrations per second); absorbed dose in grays (Gy), and dose equivalents in sieverts (Sv), which account for biological effect.

Health effects depend on dose, rate, and tissue sensitivity. Ionizing radiation can damage DNA and cellular components, potentially causing cancer or acute radiation syndrome at high doses. Non-ionizing radiation can cause heating or photochemical effects but is much less likely to cause immediate tissue damage at typical exposure levels. Safety limits are set by regulatory bodies; protective measures include reducing exposure time, increasing distance, and shielding with appropriate materials.

Applications include medical imaging (X-ray, CT) and radiotherapy for cancer treatment; industrial nondestructive testing and material analysis; fundamental research in physics. For public health and environmental protection, monitoring, containment, and proper disposal of radioactive sources are essential.