UV radiation UV radiation is part of the electromagnetic (light) spectrum that reaches the earth from the sun. It has wavelengths shorter than visible light, making it invisible to the naked eye. These wavelengths are classified as UVA, UVB, or UVC. UVA rays account for up to 95% of the UV radiation reaching the Earth's surface. They are present during all daylight hours throughout the year, and can penetrate clouds and glass UVA penetrates the skin more deeply than UVB and p