Visible light (commonly referred to simply as light) is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has a wavelength in the range of about 380 nanometres to about 740 nm – between the invisible infrared, with longer wavelengths and the invisible ultraviolet, with shorter wavelengths.
Primary properties of visible light are intensity, propagation direction, frequency or wavelength spectrum, and polarisation, while its speed in a vacuum, 299,792,458 meters per second (about 300,000 kilometers per second), is one of the fundamental constants of nature. Visible light, as with all types of electromagnetic radiation (EMR), is experimentally found to always move at this speed in vacuum.
In common with all types of EMR, visible light is emitted and absorbed in tiny "packets" called photons, and exhibits properties of both waves and particles. This property is referred to as the wave–particle duality. The study of light, known as optics, is an important research area in modern physics.
In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. This article focuses on visible light. See the electromagnetic radiation article for the general term.
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Famous quotes containing the word light:
“A light he was to no one but himself.”
—Robert Frost (18741963)
“Ex oriente lux may still be the motto of scholars, for the Western world has not yet derived from the East all the light which it is destined to receive thence.”
—Henry David Thoreau (18171862)
“Have you ever turned toward an intellectual in a time of authentic anguish and encountered his light appraisal, or evasion, of your grief? Or turned to him in a situation of light import only to be met with a heavy, superfluous solemnity?”
—Margaret Anderson (18861973)