Definition
The portion of the electromagnetic spectrum that the human eye can detect, with wavelengths roughly between 400 and 700 nanometers. It sits between ultraviolet radiation (shorter wavelengths) and infrared radiation (longer wavelengths).
Plain English
The kind of light you can actually see with your eyes. It's a small slice of a much wider range of energy waves, most of which are invisible to us.
Context Anchor
Seen in discussions of pilot vision, aircraft lighting, runway lights, visual signals, and visibility in weather.
Derivation
From the Latin 'visibilis' meaning 'able to be seen.' The phrase 'visible light' simply names the part of the light spectrum that is visible — as opposed to ultraviolet or infrared, which are forms of light energy our eyes cannot perceive.
Why Pilots Care
Pilots rely on visible light to spot terrain, other aircraft, runway markings, and beacons, especially when flying under visual flight rules.
Grounding Statement
At night, a runway light helps the pilot because it gives off visible light that the pilot’s eyes can detect.
Intuition Check
Visible light does not mean every kind of energy or signal an instrument can detect. It means the narrow part of light energy that human eyes can see directly.
Example Sentence 1
Strobe lights and navigation lights produce visible light so other pilots can see the aircraft at night.
Example Sentence 2
On a clear day the amount of visible light allowed the student to easily identify checkpoints along the route.