Much like visible light, ultraviolet light comes in a wide range of wavelengths along a spectrum. The specification most important here is found in nanometers (nm), Ultraviolet output comes from wavelengths within the 100nm to 400nm range. Ultraviolet light is characterized into 3 main groupings which help us be more specific with the type of UV light, as the characteristics change depending on the wavelength:
UV-A: 315-400nm
UV-B: 280-315nm
UV-C: 100-280nm
The most common ultraviolet lights you will come across tend to be in the UV-A region and are most commonly referred to as “blacklights”. This is the weakest form of ultraviolet light and is used for applications like UV curing and blacklight artwork.
UV-B has a shorter wavelength and is therefore a little stronger than UV-A. UV-A and UV-B are both present in natural sunlight but UV-B is the primary wavelength that causes sunburn. Both UV-A and UV-B LEDs are very limited in their ability to sterilize and eliminate viruses and bacteria.
UV-C is the portion of the spectrum you want to focus in on when looking at creating a sterilization system using ultraviolet LEDs. The higher the wavelength in this 100-280nm range the better, wavelengths specifically within 200-280nm range are sometimes referred to as Germicidal UV (GUV). Unlike UV-A and UV-B, UV-C wavelengths are blocked or absorbed by the ozone layer and atmosphere, so they do not make their way down to us on the earth’s surface. This is important as UV-C is the best light in destroying micro-organisms but also the most dangerous to human health. With no way to harness the natural UV-C rays, we are forced to look for an artificial source of UV-C light.
