Ultraviolet radiation is one form of radiant energy coming from the sun.
The ozone layer provides a defence against UV radiation reaching Earth, but several other factors also affect how UV penetrates our atmosphere. There are three categories of UV radiation. UV-A is the least damaging form of UV radiation and reaches the Earth in greatest quantity. Fortunately, most of the surfs UV-B radiation is absorbed by ozone in the stratosphere. UV-C radiation is potentially the most damaging because it is very energetic.