Ultraviolet radiation: Invisible rays that are part of the energy that comes from the sun. Ultraviolet radiation can burn the skin and cause skin cancer.
Ultraviolet radiation is made up of three types of rays -- ultraviolet A, ultraviolet B, and ultraviolet C. Although ultraviolet C is the most dangerous type of ultraviolet light in terms of its potential to harm life on earth, it cannot penetrate earth's protective ozone layer. Therefore, it poses no threat to human, animal or plant life on earth.