Final answer:
Approximately 1% of the sun's ultraviolet radiation reaches Earth's surface.
Step-by-step explanation:
The percentage of the sun's ultraviolet (UV) radiation that reaches Earth's surface is approximately 1%. Solar UV radiation is broadly subdivided into three regions: UV-A, UV-B, and UV-C, with UV-A making up 99% of the solar UV radiation reaching the Earth's surface. Most UV-B and all UV-C are absorbed by ozone molecules in the upper atmosphere, reducing the amount that reaches the surface.