Electromagnetic radiation between 8*10^14 to 3*10^16 Hz (800 THz to 30 PHz) and wavelengths from 10^-8 m to 3.8*10^-7 m (10 nm to 380 nm) are ultraviolet rays. The frequency of waves is inversely proportional to their wavelengths.
Just as visible light is composed of different wavelengths of light, ultraviolet light is divided into three different categories. UVA rays have wavelengths that are between 400 nanometers and 320 nanometers. Rays with wavelengths of 320 nanometers to 290 nanometers are UVB rays, and UVC rays have wavelengths between 290 and 10 nanometers. UVC radiation is blocked by the ozone layer, and both UVA and UVB contribute to skin cancer.