- Ultraviolet (UV) light is a form of electromagnetic radiation that lies between visible light and X-rays in the electromagnetic spectrum.
- It has shorter wavelengths than visible light, ranging from approximately 10 to 400 nanometers (nm), and therefore carries more energy. UV light is invisible to the human eye, but it plays a crucial role in both natural and artificial processes, with effects that can be beneficial or harmful depending on its intensity, exposure time, and wavelength.
- UV radiation is commonly divided into three main categories based on wavelength: UV-A (320–400 nm), UV-B (280–320 nm), and UV-C (100–280 nm). UV-A, the least energetic and longest in wavelength, constitutes about 95% of the UV radiation reaching Earth’s surface. It penetrates deep into the skin and contributes to skin aging and long-term cellular damage. UV-B has more energy and is mostly absorbed by the ozone layer, though some reaches the surface. It is responsible for sunburn and has a strong link to skin cancers. UV-C is the most energetic and dangerous form of UV radiation, but fortunately, it is completely absorbed by the Earth’s atmosphere and does not reach the surface under natural conditions.
- Ultraviolet light has numerous applications across science, industry, and medicine. In biology and medicine, UV light is used for sterilization and disinfection because it can destroy the DNA and RNA of bacteria, viruses, and other pathogens. UV-C lamps, for instance, are widely used in hospitals, laboratories, and water treatment systems for germicidal purposes. In forensics, UV light is used to detect bodily fluids, fibers, and counterfeit items. UV radiation is also critical in vitamin D synthesis in human skin, where UV-B photons catalyze the conversion of 7-dehydrocholesterol to pre-vitamin D₃, an essential process for calcium metabolism and bone health.
- However, excessive exposure to UV radiation can have detrimental effects. Prolonged UV exposure can damage living tissues, leading to sunburn, eye damage (such as cataracts), immune suppression, and an increased risk of skin cancers, including melanoma. As a result, sunscreens, protective clothing, and UV-blocking sunglasses are widely recommended for individuals who spend time outdoors. The ozone layer plays a critical role in filtering UV-B and UV-C radiation, and damage to this layer (such as the ozone hole) has raised significant environmental and public health concerns.
- From a physical perspective, UV light also causes fluorescence in certain substances, making them emit visible light when exposed to UV radiation. This phenomenon is used in a variety of applications, from mineral identification and currency verification to entertainment lighting and art restoration. Furthermore, UV light is extensively used in astronomy, where UV telescopes observe the high-energy processes of the universe, such as star formation and the behavior of hot gases in galaxies.
