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:
“Separated lovers cheat absence by a thousand fancies which have their own reality. They are prevented from seeing one another and they cannot write; nevertheless they find countless mysterious ways of corresponding, by sending each other the song of birds, the scent of flowers, the laughter of children, the light of the sun, the sighing of the wind, and the gleam of the starsall the beauties of creation.”
—Victor Hugo (18021885)
“Go out of the house to see the moon, and t is mere tinsel; it will not please as when its light shines upon your necessary journey. The beauty that shimmers in the yellow afternoons of October, who could ever clutch it? Go forth to find it, and it is gone: t is only a mirage as you look from the windows of diligence.”
—Ralph Waldo Emerson (18031882)
“The light that never was, on sea or land,
The consecration, and the Poets dream;”
—William Wordsworth (17701850)