Ultraviolet waves are electromagnetic waves whose wavelengths fall under the ultraviolet spectrum. These waves cannot be detected by the human eye but their effects can be observed with the help of fluorescent substances. The wavelength of a typical ultraviolet wave lies in the range of 10 nanometres to 400 nanometres. Ultraviolet radiation is further subcategorized into near-ultraviolet radiation (whose wavelength ranges from 300 to 400 nanometres), middle-ultraviolet radiation (whose wavelength ranges from 200 to 300 nanometres), far-ultraviolet radiation (whose wavelength ranges from 100 to 200 nanometres), and extreme ultraviolet radiation (whose wavelength is below 100 nanometres).
Common examples of ultraviolet radiation include UVA radiation (wavelength range: 315-400 nanometres), UVB radiation (wavelength range: 280-315 nanometres), and UVC radiation (wavelength range: 100-280 nanometres). Of all the ultraviolet waves that originate from the sun and arrive on the Earth’s surface, approximately 99% is UVA waves