What is UV?

UV stands for ultraviolet.  It is a higher energy spectrum than visible light with wavelengths between 100 nm to 400 nm.  Based on the International Union of Pure and Applied Chemistry (IUPAC)’s definition (https://goldbook.iupac.org/terms/view/UT07492): 

UV-A: 315-400 nm 

UV-B: 280-315 nm 

UV-C: 200-280 nm 

VUV (Vacuum UV): 100-200 nm