| infrared rays | That portion of the electromagnetic spectrum usually sensed as heat. Infrared wavelengths are longer than those of visible light, extending into the microwave frequencies. They are used therapeutically as heat, and also to warm food in restaurants. (12 Dec 1998) |
|---|---|
| intermediate rays | Those between ultraviolet and X-ray's. Synonym: W rays. (05 Mar 2000) |
| ultrasonic rays | See: ultrasonic. (05 Mar 2000) |
| ultraviolet rays | That portion of the electromagnetic spectrum immediately below the visible range and extending into the X-ray frequencies. The longer wavelengths (near-uv or biotic or vital rays) are necessary for the endogenous synthesis of vitamin d and are also called antirachitic rays; the shorter, ionizing wavelengths (far-uv or abiotic or extravital rays) are viricidal, bactericidal, mutagenic, and carcinogenic and are used as disinfectants. (12 Dec 1998) |