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ULTRAVIOLET: invisible light rays emitted by the sun that are just beyond the visible spectrum.

ULTRAVIOLET-A RAYS: (UVA rays) the longest ultraviolet light rays emitted by the sun, causing damage to the epidermis and the dermis of the skin and to the eyes over long periods of exposure.

ULTRAVIOLET-B RAYS: (UVB rays) the mid-lenght ultraviolet light rays emitted by the sun, causing damage to the epidermis and the dermis of the skin and which may also be harmful to the eyes.

ULTRAVIOLET-C RAYS: (UVC rays) the shortest ultraviolet light rays emitted by the sun. If these rays were not absorbed by the ozone layer they would cause severe bodily harm.

XANTHINES: a group of stimulants, including theobromine and caffeine, that may be found in chocolate, coffee, and tea causing dilation of blood vessels and stimulation of the muscles, especially the heart.