A Wood's lamp is a source of ultraviolet radiation of wavelengths centered around 3,650 Angstrom units, and ranging from approximately 3,200 A to 4,000 A. It thus excludes most of the burning and tanning rays shorter than 3,200 A and the visible light rays longer than 4,000 A. This portion of the electromagnetic spectrum is also called long-wave ultraviolet, near ultraviolet, or blacklight.
For many years it has been known that near ultraviolet will excite fluorescence of a great many substances, a fact much exploited in advertising, industry, and general scientific investigations. Physicians and medical investigators have also used this type of energy to help understand some of the biologic processes that concern them. Such uses are the subject of this paper.
Although one may employ complicated and powerful equipment plus precise and expensive filters to obtain greater precision of wavelength and higher energy levels, most Wood's lamps fortunately are