Ultraviolet (UV) radiation is electromagnetic radiation with wavelengths shorter than visible light. Sunlight is a major source, and UV exposure can degrade plastics, coatings, and other materials. Lens and housing materials may therefore be tested or treated for UV resistance. UV output and UV resistance are separate properties. UV-A, UV-B, and UV-C occupy different wavelength ranges and have different sources and effects. Outdoor equipment is mainly exposed to solar UV, which can cause fading, embrittlement, yellowing, or loss of coating performance over time. Accelerated weathering tests help compare material resistance, but the method and exposure conditions must be stated.