Wood’s lamp [Robert W. Wood, American physicist, 1868–1955; AS, glaes] , an illuminating device with a nickel oxide filter that holds back all light except for a few violet rays of the visible spectrum and ultraviolet wavelengths of about 365 nm. It is used extensively to help diagnose fungal infections of the scalp and erythrasma. The light causes hairs infected with a fungus such as Tinea capitis to become brilliantly fluorescent. Also called black light.
