ultraviolet rays

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 ( see ozone ). If this did not happen, the intense ultraviolet radiation from the sun would be lethal to living organisms.