Visible light is a term used to describe the portion of the electromagnetic spectrum that can be detected by human eyes, typically wavelengths between 400 and 700 nm. See also UV (ultraviolet radiation) light, X-ray and microwaves.
Human eyes visibility
Humans see around three per cent of the energy, in the middle of the spectre, since microwaves, radioactivity etc. is dangerous on both sides of the visible spectrum, short and long wavelengths of energy (light). See Ultraviolet Radiation (UV) and Light reflectance