radiation

The emission and propagation of energy as electromagnetic waves or subatomic particles.

• electromagnetic spectrum: radio, microwave, infrared, visible light, ultraviolet, X-ray, gamma
• visible light occupies a narrow band — perception mapped in color-emotion spectrum
• ionizing radiation (UV, X-ray, gamma) carries enough energy to strip electrons from atoms
• thermal radiation: every body above absolute zero emits radiation determined by temperature
• blackbody spectrum led Planck to quantize energy — birth of quantum mechanics
• electromagnetism describes the field dynamics of all electromagnetic radiation
• particle radiation: alpha, beta, neutron — products of nuclear force interactions
• cosmic radiation from stars and the cosmic microwave background pervades spacetime — see cosmology