Light

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.

Read more about Light:  Speed of Visible Light, Electromagnetic Spectrum and Visible Light, Optics, Light Sources, Units and Measures, Light Pressure

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... discovered that the plane of polarisation of linearly polarised light is rotated when the light rays travel along the magnetic field direction in the presence of a ... 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 ...
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... is greater than c would contradict the concept of local time (based on synchronization by light signals) and the principle of relativity ... we could communicate by signals other than those of light, the velocity of propagation of which differed from that of light? If, after having regulated our ... 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 with the speed of light ...
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... The CIE color rendering 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 source ... a numerical estimate of what reference (ideal) light source best approximates a particular artificial light, and what the difference is ...
Flash - Light
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Famous quotes containing the word light:

    A light exists in spring
    Not present on the year
    At any other period.
    Emily Dickinson (1830–1886)

    The light of heaven falls whole and white
    And is not shattered into dyes....
    Robert Frost (1874–1963)

    Lady of light, I would admit a dream
    To you, if you would take it in your hand.
    Will you not let it in a gentle stream
    Of living blood? How else may I remand
    Your light if not as pulse upon your ear?
    Allen Tate (1899–1979)