UV-A light is known as “dark-light” and, because of its longer wavelength, can penetrate most windows. It also penetrates deeper into the skin than UV-B light and is thought to be a prime cause of wrinkles. UV-A rays are a suspect in the development of cataracts, and might contribute to macular degeneration and aging of the retina.
UV-B light is recognized as a harmful, destructive form of UV light that causes sunburn, skin cancer and damage to the eye including cataracts and macular degeneration.
UV-C rays are the strongest, most dangerous type of ultraviolet light. However, UV-C rays are normally filtered out by the ozone layer and do not reach the Earth.