Editing Ultraviolet (section)

=== "Black lights" ===
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| image1            = Two black light fluorescent tubes.jpg
| image2            = Two black light lamps.jpg
| footer            = Two black light fluorescent tubes, showing use. The longer tube is a F15T8/BLB 18&nbsp;inch, 15&nbsp;watt tube, shown in the bottom image in a standard plug-in fluorescent fixture. The shorter is an F8T5/BLB 12&nbsp;inch, 8&nbsp;watt tube, used in a portable battery-powered black light sold as a pet urine detector.
}}

{{Main|Blacklight}}
A ''black light'' lamp emits long-wave UVA radiation and little visible light. Fluorescent black light lamps work similarly to other [[fluorescent lamps]], but use a [[phosphor]] on the inner tube surface which emits UVA radiation instead of visible light. Some lamps use a deep-bluish-purple [[Wood's glass]] optical filter that blocks almost all visible light with wavelengths longer than 400&nbsp;nanometers.<ref>
{{cite web
 |title=Insect-O-Cutor
 |url=http://www.insect-o-cutor.com/ioclibrary/blacklight.pdf
 |url-status=live
 |archive-url=https://web.archive.org/web/20130604215247/http://www.insect-o-cutor.com/ioclibrary/blacklight.pdf
 |archive-date=4 June 2013
}}
</ref> The purple glow given off by these tubes is not the ultraviolet itself, but visible purple light from mercury's 404&nbsp;nm spectral line which escapes being filtered out by the coating. Other black lights use plain glass instead of the more expensive Wood's glass, so they appear light-blue to the eye when operating.{{cn|date=May 2024}}

Incandescent black lights are also produced, using a filter coating on the envelope of an incandescent bulb that absorbs visible light (''see section below''). These are cheaper but very inefficient, emitting only a small fraction of a percent of their power as UV. [[mercury vapor lamp|Mercury-vapor]] black lights in ratings up to 1&nbsp;kW with UV-emitting phosphor and an envelope of [[Wood's glass]] are used for theatrical and concert displays.{{cn|date=May 2024}}

Black lights are used in applications in which extraneous visible light must be minimized; mainly to observe ''[[fluorescence]]'', the colored glow that many substances give off when exposed to UV light. UVA / [[UV-B lamps|UVB emitting bulbs]] are also sold for other special purposes, such as [[tanning lamp]]s and reptile-husbandry.{{cn|date=May 2024}}