Ultraviolet rays are part of the electromagnetic spectrum and have both positive and negative effects on humans and other organisms. Overexposure can lead to health problems such as skin cancer and cataracts. UV rays are used in medical therapy, industrial and commercial applications, and can be filtered by natural substances such as the ozone layer.
Ultraviolet rays are part of the electromagnetic spectrum which includes visible light and other forms of natural radiation, such as microwaves and radio waves. Their wavelength is positioned just beyond violet light on this spectrum; hence their name. Ultraviolet rays are invisible to the naked eye, but have a wide range of physical effects. These include chemical reactions and both positive and negative health effects on humans and other organisms. The Earth’s natural ozone layer filters out very harmful ultraviolet (UV) radiation.
Many forms of electromagnetic radiation are emitted by the sun and other natural sources of energy. The most familiar form of this radiation is visible light, but other invisible forms of radiation are emitted by these same sources. The position of this radiation in the electromagnetic spectrum is determined by its wavelength. Long wavelength light is reddish in color, and just beyond the red end of the visible spectrum is infrared (IR) radiation. At the opposite end of the visible spectrum, with a slightly shorter wavelength than blue and violet light, are ultraviolet rays.
Ultraviolet rays are in turn divided into several categories, according to their wavelength and their effects on human health. The ultraviolet radiation closest to visible light is classified as UVA, UVB and UVC, while that closest to X-ray radiation is called extreme ultraviolet (EUV). In humans, exposure to UVB rays promotes the production of vitamin D, an essential nutrient that aids the immune system. Various forms of UV radiation are used in medical therapy, including the treatment of skin conditions and nutritional deficiencies such as rickets.
Overexposure to ultraviolet rays, however, can lead to serious health problems. UV radiation causes a tan, as the skin produces melanin, a darkening agent, to filter out UV radiation. Prolonged exposure, however, can increase your risk of medical problems like skin cancers and cataracts; for this reason, manufacturers of sunscreens and sunglasses emphasize their UV filtering properties. Various natural substances also filter harmful UV radiation, including glass, the earth’s atmosphere and the ozone layer. It is believed that the depletion of the ozone layer can lead to an increase in health problems caused by UV rays.
Ultraviolet rays have numerous industrial and commercial applications. They can be used to detect chemical signatures, both those placed deliberately, such as on passports and money, and those created naturally by substances such as animal waste. Concentrated UV light is an effective germicide, as many harmful microorganisms cannot tolerate this form of radiation. Scientists use ultraviolet light for analytical purposes in fields ranging from forensics to astronomy. Inks that fluoresce, or glow, under UV light are used to create “black light” posters, clothing and makeup.
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