UV light is part of the electromagnetic spectrum that is outside the visible light portion. It has a lower wavelength and is invisible to the human eye.
UV light is categorized into three parts:
UV-A makes up 95% of the UV-A radiation that reaches the Earth. It ranges from 320nm-400nm in wavelength. UV-A causes skin aging.
UV-B is the other UV radiation that makes up sunlight. The wavelength of UV-B ranges from 280nm-320nm. UV-B causes sunburns.
UV-C from the sun is absorbed and blocked by earths atmosphere. UV-C wavelength is 100nm-280nm.