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.
Other articles related to "light":
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Famous quotes containing the word light:
“Poor Casey Jones he was all right,
He stuck by his duty both day an night,”
—Unknown. Casey Jones. . .
Oxford Book of Light Verse, The. W. H. Auden, ed. (1938)
“But misery still delights to trace
Its semblance in anothers case.
No voice divine the storm allayd,
No light propitious shone;
When, snatchd from all effectual aid,
We perishd, each alone:
But I beneath a rougher sea,
And whelmd in deeper gulphs than he.”
—William Cowper (17311800)
“I think continually of those who were truly great.
Who, from the womb, remembered the souls history
Through corridors of light where the hours are suns,
Endless and singing.”
—Stephen Spender (19091995)