It all started when...
1. something that makes things visible or affords illumination:
All colors depend on light.
- Also called luminous energy, radiant energy. electromagnetic radiation to which the organs of sight react, ranging in wavelength from about 400 to 700 nm and propagated at a speed of 186,282 mi./sec (299,972 km/sec), considered variously as a wave, corpuscular, or quantum phenomenon.
- a similar form of radiant energy that does not affect the retina, as ultraviolet or infrared rays.
the sensation produced by stimulation of the organs of sight