Scientifically put, ultraviolet light refers to the region of the electromagnetic spectrum between visible light and X-rays. This electromagnetic spectrum is not visible to the human eye because it has a shorter wavelength and a higher frequency than the light our brain perceives as images. An easy way to remember UV light’s placement: Red is the light with the longest wavelength, and Violet is the light with the shortest wavelength. Therefore, light with a wavelength longer than any light in the visible spectrum is called Infrared Light, and light with a wavelength immediately shorter than any light in the visible spectrum is called Ultraviolet Light.
UV-A and UV-B light cause sunburns and premature skin aging, and exposure to both is associated with the development of skin cancer. UV-C light, which has the most energy of all three types of UV light, is the most harmful, but it fortunately doesn’t reach the Earth’s surface because our atmosphere absorbs it. UV-A has tanning properties: UV light with the longest wavelength, and the least harmful. It is more commonly known as “black light”, and many use its ability to cause objects to emit fluorescence (a colored glowing effect) in artistic and celebratory designs. Many insects and birds can perceive this type of UV radiation visually.
UV-B has therapeutic and vitamin “D” synthesizing properties: causes sunburns with prolonged exposure along with increased risk of skin cancer and other cellular damage. About 95% of all UV-B light is absorbed by the ozone in Earth’s atmosphere.
There’s man-made UV-C light, too: It’s what’s in the UV lights that companies claim kill coronaviruses. According to the National Academy of Sciences, it’s probable that this is true, because UV light has been used to disinfect surfaces and water for a long time, and it’s generally successful. UV-C has germicidal properties: this type of UV light is extremely harmful and is almost completely absorbed by Earth’s atmosphere. It is commonly used as a disinfectant in food, air, and water to kill microorganisms by destroying their cells’ nucleic acids.
Want to know more information about UV-C rays and how they work? Check out this post for more in-depth details.