black theatre / teatro negro / noir théâtre / schwarzes theater / bigio teatro / kara tyiatro /  黑剧院 / ساحة سوداء / 까만 극장 / 黒い劇場 / שחור תיאטרון / 

...if you turn on a black light bulb in a dark room, what you can see from the bulb is a purplish glow. What you cannot see is the ultraviolet light that the bulb is also producing. Our eyes can see visible light in a spectrum ranging from red through orange, yellow, green, blue and violet. Above violet is ultraviolet light, which we cannot see. A black light bulb produces UVA light (as opposed to UVB light, which is much more harmful). A "black light" or Ultraviolet lamp is almost the same as the flourescent lights used in most classrooms. The difference is that "UV" lights lack the white phosphor coating, and they are made with dark blue glass. Flourescent tubes contain a near vacuum with a little mercury vapor.

What you see glowing under a black light, whether on a fluorescent poster or an invisible hand stamp or a newly washed white T-shirt, are phosphors. A phosphor is any substance that emits visible light in response to some sort of radiation. A phosphor converts the energy in the UV radiation from a black light into visible light. In the next section, we'll see how phosphors are used in regular fluorescent lighting and in black lights. White T-shirts and socks normally glow under a black light because modern detergents contain phosphors that convert UV light into white light. This makes whites look "whiter than white" in normal sunlight. What you are seeing in sunlight is the normal reflection of visible white light from the cloth, as well as the emission of white light that the phosphors create from UV light in sunlight. The T-shirt really is whiter than white!

There are lots of natural phosphors, in your teeth and fingernails, among other things. There also a lot of phosphors in manmade material, including television screens and some paints, fabric and plastics. Most fluorescent colored things, such as highlighters, contain phosphors, and you'll find them in all glow-in-the-dark products. Clubs and amusement parks use special black light paint that glows different colors. You can also buy fluorescent black light bubbles, invisible black light ink, fluorescent black light carpet and even fluorescent black light hair gel.
Appraisers use them to detect forgeries of antiques. Many paints today contain phosphors that will glow under a black light, while most older paints do not contain phosphors. Repairmen use them to find invisible leaks in machinery -- they inject a little fluorescent dye into the fuel supply and illuminate it with a black light. For example, they might detect an invisible air conditioner leak by adding fluorescent dye to the refrigerant. Law enforcement officers can use them to identify counterfeit money.
The United States and many other countries include an invisible fluorescent strip in their larger bills that only shows up under a black light.musement parks and clubs use them to identify invisible fluorescent hand stamps for readmission. Forensic scientists use them to analyze crime scenes. To pick out fingerprints, for example, they often dust with fluorescent dye under a black light. This makes it easier to pick the fingerprints out from surrounding dirt. Black lights can also identify semen and other bodily fluids that naturally fluoresce…