What is a good effect of ultraviolet radiation?
UV light is found in sunlight. The entire spectrum of ultraviolet radiation has some of the biological features of ionizing radiation. It does far more damage to many molecules in biological systems than is accounted for by simple heating effects.
Ultraviolet photon's power is to alter chemical bonds in molecules, even without having enough energy to ionize atoms.
Life on Earth outside of the deep oceans is possible only because the atmosphere, primarily the ozone layer, filters out the vast majority of this light.
Ultraviolet is also responsible for the formation of vitamin D in organisms that make this vitamin (including humans). This vitamin has regulatory roles in calcium metabolism (which is vital for normal functioning of the nervous system, as well as for bone growth and maintenance of bone density), immunity, cell proliferation, insulin secretion, and blood pressure.
Some other uses are:
Disinfecting of drinking water
Treatment of some skin diseases such as psoriasis.