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":
... This was the first evidence that light was related to electromagnetism ... In 1846 he speculated that light might be some form of disturbance propagating along magnetic field lines ... Faraday proposed in 1847 that light was a high-frequency electromagnetic vibration, which could propagate even in the absence of a medium such as the ether ...
... a single-use source of very short and extremely bright flashes of light Arc flash, an electrical explosion Lightning, a natural phenomenon Muzzle flash, the visible light ...
... c would contradict the concept of local time (based on synchronization by light signals) and the principle of relativity ... communicate by signals other than those of light, the velocity of propagation of which differed from that of light? If, after having regulated our watches ... is transmitted with a velocity a million times as great as that of light? However, in 1905 Poincaré calculated that changes in the gravitational field can propagate ...
... Black body radiators are the reference by which the whiteness of light sources is judged ... By analogy, nearly-Planckian light sources such as certain fluorescent or high-intensity discharge lamps can be judged by their correlated color temperature (CCT) the color temperature of the Planckian ... The question is what is the relationship between the light source's relative spectral power distribution and its correlated color temperature? ...
... index (CRI) is a method to determine how well a light source's illumination of eight sample patches compares to the illumination provided by a reference ... estimate of what reference (ideal) light source best approximates a particular artificial light, and what the difference is ...
Famous quotes containing the word light:
“I see my light come shining
From the west unto the east
Any day now, any day now,
I shall be released.”
—Bob Dylan [Robert Allen Zimmerman] (b. 1941)
“A light exists in spring
Not present on the year
At any other period.”
—Emily Dickinson (18301886)
“Erasmus was the light of his century; others were its strength: he lighted the way; others knew how to walk on it while he himself remained in the shadow as the source of light always does. But he who points the way into a new era is no less worthy of veneration than he who is the first to enter it; those who work invisibly have also accomplished a feat.”
—Stefan Zweig (18811942)