UV light is a range of wavelengths just above visible light. It has subcategories including near, medium, far, blank, and extreme. It is emitted by the sun and can cause sunburn and skin cancer, but is also important for vitamin D production.
When people refer to ultraviolet (UV) light, they usually mean the UV spectrum. A spectrum is a range of wavelengths rather than a specific wavelength. The UV spectrum is only a portion of the entire electromagnetic (EM) spectrum; it is just above visible light if the different categories have been classified according to energy. There are numerous subcategories of UV radiation, including near, medium, far, blank, and extreme. UV light is important to human health because it is a major source of vitamin D, but it can also increase health risks, such as skin cancer.
The electromagnetic spectrum is a system used to describe light of different wavelengths. Visible light is only part of the spectrum, ranging from low-energy radio waves to high-energy gamma rays. The UV spectrum has a shorter wavelength and higher frequency than visible light and is higher in energy. However, UV light is not just part of a single wavelength; the UV spectrum ranges from a wavelength of about 10 nanometers (nm) to 400 nm.
This wavelength range is called ultraviolet because it lies just above the visible-violet light section of the EM spectrum. Within the UV spectrum, there are a number of further subsections. Near UV, for example, is closest to violet light and includes radiation up to a wavelength of 315 nm. Extreme UVs are at the other end of the spectrum and contain radiation between 121nm and 10nm. The lower the wavelength, the higher the energy and frequency of the UV light.
Light within the UV spectrum is emitted by the sun. Sunlight contains UV radiation in a range of frequencies, which is why it is referred to as a spectrum. UV rays are made up of radiation of higher energy than visible light, which is why they can cause sunburn. Some types of fluorescent lamps can also provide artificial UV radiation.
UV radiation can have both positive and negative health effects. Exposure to UV rays is essential for the body to produce vitamin D, for example a nutrient that is difficult to obtain from diet alone. UV light is also sometimes used to treat skin conditions, such as psoriasis, although this form of treatment should be monitored closely to avoid harm. Many people also use UV rays to get a more tanned look. However, overexposure to this wavelength of light can cause skin cancer.
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