Black lights are UV-A lights that emit only a little visible light, with most of the light they emit being the so-called black light. The violet filter material of the lamp blocks most of the visible light and lets only the UV light come through. These lights have several great uses, as in amusement parks and nightclubs.
In nightclubs and amusement parks, black lights help to create a visually appealing effect. They make white clothes glow in the dark, for instance. When you combine black lights with fluorescent black light carpet, invisible black light ink, glow in the dark paint that only shows in this UV light, or black light hair gel you can achieve amusing effects. Many entertainment venues use black lights to detect fluorescent hand stamps that they use as admission tickets for events.
Many repair people use black light bulbs in order to find invisible leaks in machinery. By injecting a small amount of fluorescent dye into the fuel supply and illuminating it with black lights, it is possible to spot leaks in the smallest parts. By mixing the dye with refrigerant, you can find leaks in an air conditioner.
Identifying Counterfeit Money
Law enforcement officers benefit from black lights when trying to find counterfeit money. Many countries include a fluorescent strip in their banknotes that is visible only under black lights. If the banknote lacks that specific strip, the money is fake. These stripes are mainly on larger, more valuable bills. Many antique appraisers also use black lights to distinguish fake paintings from originals. Antique paintings do not contain phosphors that glow under black lights, while you can find these in newer artworks that are actually counterfeit.
Analysing Crime Scenes
Forensic experts make use of black lights when analysing crime scenes. Scientists often dust the area with fluorescent dye and then shed light on it. The fingerprints then glow. Therefore, it is rather easy to pick fingerprints out from surrounding dirt. Black lights are also useful for identifying bodily fluids that are already naturally fluorescent.
Diagnosing Infections and Poisoning
Many fungal and bacterial infections, such as pseudomonas and microsporum audouinii, glow in the dark. In dermatology, doctors shine a Wood's lamp onto the patient's skin to detect various diseases. Different bacteria and fungi have different colours. For instance, porphyrin glows pink, while acne bacteria glow orange.