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.
Famous quotes containing the word light:
“Come, and trip it as ye go
On the light fantastic toe,
And in thy right hand lead with thee,
The mountain nymph, sweet Liberty;”
—John Milton (16081674)
“I learn to affirm
Truths light at strange turns of the minds road,
wrong turns that lead
over the border into wonder....”
—Denise Levertov (b. 1923)
“Her mane falls wild on her forehead,
And the light breeze moves me to caress her long ear
That is delicate as the skin over a girls wrist.
Suddenly I realize
That if I stepped out of my body I would break
—James Wright (19271980)