Electromagnetic waves in the region of optical frequencies. The term "light" was originally restricted to
radiation visible to the human eye, with wavelengths between 400 and 700 nm. However, it has
become customary to refer to Radiation in the spectral regions adjacent to visible Light (in the near
infrared from 700 to 2,000 nm) as light in order to emphasize the physical and technical characteristics
they have in common with light.