What is UV light?
How is UV light produced?
Ultraviolet (UV) light is between visible light and x-rays on the electromagnetic spectrum. It is broken up into sub-sections, the main ones being UVA, UVB and UVC.
UVA has the longest wavelength and UVC has the shortest. The Sun produces a large amount of UV light in all bands, but the Earth’s atmosphere blocks most of UVB and UVC. This is good because large amounts of UV light can cause sunburn and can increase your risk of developing skin cancer. Sun beds also use UV light to give you a tan, therefore it is advisable not to overuse sunbeds, and to wear sunscreen when you know you’ll be out in a Sun for a long period of time. However, everyone is different so some people will burn more easily than others. Despite this, low levels of UV light is actually beneficial for you as it helps produce vitamin D in your body which is crucial for keeping your bones healthy.
UV light is also used within a variety of industries for its ability to kill harmful microbes which is useful, specifically in the medical sector, when sterilising medical equipment and even the air. [UV1]
Ultraviolet (UV) light can be produced using special lamps, however different types of UV light require different lamp designs. Longer UV light, UVA, is produced by using a fluorescent lamp. Traditional fluorescent light bulbs work by ionising mercury vapour by putting a large voltage across it. This causes the electrons in mercury to change energy levels, and by doing so they emit photons in the UV part of the spectrum.
In normal fluorescent lights, they have a phosphor coating which absorbs the UV light and re-emits it as visible light. For the case of wanting to produce UV light, a different type of phosphor coating is used or no coating at all which allows it to pass through. To produce UVA a phosphor coating would be used that emits UV light instead of visible light. However, as this is longer UV light, it is very near the blue part of visible light which is why some UV lights you see appear purple - blue. To produce shorter range UV light, UVC, a no phosphor coating would be used, as the fluorescent light naturally produces UV light in this range. [UV1]