Introduction to ultraviolet rays contained in light sources
Natural daylight and many artificial light sources contain a certain amount of ultraviolet radiation. Ultraviolet radiation intensity is generally measured in standard power units (SPUs), meaning radiant flux is measured in watts and irradiance is measured in watts per square meter. UV illuminance is calculated using the same method as illuminance.
For ease of reference, the International Commission on Illumination (CIE) divides the ultraviolet spectrum into three ranges:
Range from 400 to 315 nanometers is called near-ultraviolet (UV-A); from 315 to 280 nanometers is called mid-ultraviolet (UV-B); and from 280 to 100 nanometers is called far-ultraviolet (UV-C).