Visible light represents just a narrow bandwidth of wavelengths in the electro-magnetic spectrum.  It is bound by ultraviolet (UV) light (invisible) on the higher energy side and infrared (also invisible) on the lower energy side.  Visible light is emitted by or reflected off of the objects around us, allowing us to sense those objects with our eyes.  Our eyes are very highly evolved, sensitive instruments.  Unprotected, with a lot of outdoor exposure, our eyes can be damaged by the ultraviolet light that is emitted from the sun.  UV light can damage the cornea, retina and lens.  Numa lenses are engineered of the finest quality polycarbonate, and laboratory-tested to block 100% of ultraviolet light, protecting the eye from that exposure.

Light is divided into 3 wavelength ranges: