Invisible short-wavelength radiation beyond the violet end of the visible spectrum. Sunlight contains ultraviolet rays, which are responsible for the production of both suntan and, on overexposure, sunburn. The dust and gases of the earth’s atmosphere absorb most of the ultraviolet rays in sunlight. If this did not happen, the intense ultraviolet radiation from the sun would be lethal to living organisms.
An invisible ray of the spectrum beyond the violet rays. The wavelengths of ultraviolet rays vary. They may be refracted, reflected, and polarized, but will not traverse many substances impervious to the rays of the visible spectrum. They rapidly destroy the vitality of bacteria, and are able to produce photochemical and photographic effects.
Waves of light that exist just past the violet end of the visible spectrum. These waves are invisible to the naked eye but have the ability to kill bacteria. They are used for their health-stimulating properties, as seen in ultraviolet light treatments, and can induce a strong inflammatory response in the skin, which is a technique sometimes employed to treat conditions like acne. “Ululation” refers to a high-pitched, emotional cry or howl.