Ultraviolet (UV) light has many useful features. It carries more energy than visible light, making it a potent germ killer. It causes certain substances to glow, aiding in crime detection and making colorful displays. Its energy causes the tanning reaction in human skin; tanning beds use artificial UV light to let you get a tan in winter months. UV triggers other chemical reactions, allowing manufacturers to glue parts together with greater precision. Semiconductor makers harness the short wavelength of UV light to make more powerful computer chips.
Tanning beds have an array of UV lamps inside. Exposing your skin to certain kinds of UV light causes it to turn darker. The lamps in the beds give off UV light similar to UV rays found in sunlight.
Used to create a dramatic ambience, black lights give off a safe form of UV light. The UV light from a black light causes some materials to fluoresce, or glow in bright colors. Posters made with fluorescent ink will give off this glow, but only under a black light.
Besides entertainment, you can use a black light to detect the presence of certain chemicals and minerals that would be otherwise invisible. Two wavelengths of UV, called UVA and UVB, make different substances glow. UVA is the safer, more common black light; UVB is used more for scientific or professional study. The wavelength of UVB is shorter than that of UVA and can harm your eyes.
Germicidal UV lamps are similar to fluorescent lamps used in office lighting, but their glass is clear; they lack the phosphor coating that produces white light. These lamps give off UV light strong enough to kill microbes and are used in hospitals and other settings that need this kind of sterilization. If you see this kind of lamp, exercise caution, as direct exposure to the light can cause retinal damage and sunburn.
Other air-purifying lamps are sold for household use; these are coated to protect people from the shorter-wavelength UV light.
Special adhesives have been developed that set only when exposed to UV light. In manufacturing, it's advantageous to be able to apply adhesive on parts, align them and then cause the adhesive to set in a controlled way. The adhesive sets on demand, reducing concerns that parts might be stuck incorrectly.
Integrated circuits (ICs) have extremely detailed features. Their manufacture entails the use of photolithography, a process where a silicon wafer is photographically impressed with a pattern. The pattern is chemically developed, and the silicon is selectively etched, creating tiny electronic components. When the size of transistors on ICs shrunk past a certain point, visible light was no longer able to create the level of detail necessary. IC makers turned to UV light; since its wavelength is shorter, it can create patterns with finer details.
- Photo Credit Image by Flickr.com, courtesy of Emergency Brake
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