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60-528: [REDACTED] Look up Light  or light in Wiktionary, the free dictionary. The Light may refer to: Film [ edit ] The Light (1919 film) , a 1919 film directed by J. Gordon Edwards The Light (film) , a 2004 French film (original title: L'équipier ) The Light: Swami Vivekananda , a 2013 Indian film by Utpal Sinha Music [ edit ] The Light (producers) ,

120-404: A "pulse theory" and compared the spreading of light to that of waves in water in his 1665 work Micrographia ("Observation IX"). In 1672 Hooke suggested that light's vibrations could be perpendicular to the direction of propagation. Christiaan Huygens (1629–1695) worked out a mathematical wave theory of light in 1678 and published it in his Treatise on Light in 1690. He proposed that light

180-448: A 2008 album by Reinxeed "The Light", a song by Adam Lambert on his 2015 album The Original High "The Light", a song by Mason Jennings on his 2000 album Birds Flying Away "The Light", a song by Supreme Beings of Leisure on their 2008 album 11i "The Light", a song by Alesha Dixon on her 2009 re-release of The Alesha Show "The Light", a song by Metronomy on their 2019 album Metronomy Forever Peter Hook and

240-609: A better representation of how "bright" a light appears to be than raw intensity. They relate to raw power by a quantity called luminous efficacy and are used for purposes like determining how to best achieve sufficient illumination for various tasks in indoor and outdoor settings. The illumination measured by a photocell sensor does not necessarily correspond to what is perceived by the human eye and without filters which may be costly, photocells and charge-coupled devices (CCD) tend to respond to some infrared , ultraviolet or both. Light exerts physical pressure on objects in its path,

300-556: A body could be so massive that light could not escape from it. In other words, it would become what is now called a black hole . Laplace withdrew his suggestion later, after a wave theory of light became firmly established as the model for light (as has been explained, neither a particle or wave theory is fully correct). A translation of Newton's essay on light appears in The large scale structure of space-time , by Stephen Hawking and George F. R. Ellis . The fact that light could be polarized

360-406: A common feature of near-death experiences See also [ edit ] The Lights , American rock band The 'Lights , American TV show Light (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title The Light . If an internal link led you here, you may wish to change the link to point directly to

420-467: A force of about 3.3 piconewtons on the object being illuminated; thus, one could lift a U.S. penny with laser pointers, but doing so would require about 30 billion 1-mW laser pointers.   However, in nanometre -scale applications such as nanoelectromechanical systems (NEMS), the effect of light pressure is more significant and exploiting light pressure to drive NEMS mechanisms and to flip nanometre-scale physical switches in integrated circuits

480-411: A lasting molecular change (a change in conformation) in the visual molecule retinal in the human retina, which change triggers the sensation of vision. There exist animals that are sensitive to various types of infrared, but not by means of quantum-absorption. Infrared sensing in snakes depends on a kind of natural thermal imaging , in which tiny packets of cellular water are raised in temperature by

540-450: A medium faster than the speed of light in that medium can produce visible Cherenkov radiation . Certain chemicals produce visible radiation by chemoluminescence . In living things, this process is called bioluminescence . For example, fireflies produce light by this means and boats moving through water can disturb plankton which produce a glowing wake. Certain substances produce light when they are illuminated by more energetic radiation,

600-827: A neighbourhood in George Town, Malaysia The Light, a video game development team responsible for the game Rex The Light Cinemas , a British independent cinema chain An-Nur (The Light), 24th sura of the Qur'an Secret Society of Super Villains or "The Light", in the Young Justice animated universe The Light, an alternative name for the Assiniboine chief Wi-jún-jon The Light (drug), Dipropyltryptamine (DPT, synthetic designer drug and entheogen taken as sacrament) A tunnel of light, often called "the light",

660-424: A phenomenon which can be deduced by Maxwell's equations , but can be more easily explained by the particle nature of light: photons strike and transfer their momentum. Light pressure is equal to the power of the light beam divided by c , the speed of light.   Due to the magnitude of c , the effect of light pressure is negligible for everyday objects.   For example, a one-milliwatt laser pointer exerts

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720-419: A process known as fluorescence . Some substances emit light slowly after excitation by more energetic radiation. This is known as phosphorescence . Phosphorescent materials can also be excited by bombarding them with subatomic particles. Cathodoluminescence is one example. This mechanism is used in cathode-ray tube television sets and computer monitors . Certain other mechanisms can produce light: When

780-410: A source. One of Newton's arguments against the wave nature of light was that waves were known to bend around obstacles, while light travelled only in straight lines. He did, however, explain the phenomenon of the diffraction of light (which had been observed by Francesco Grimaldi ) by allowing that a light particle could create a localised wave in the aether . Newton's theory could be used to predict

840-414: A surface between one transparent material and another. It is described by Snell's Law : where θ 1 is the angle between the ray and the surface normal in the first medium, θ 2 is the angle between the ray and the surface normal in the second medium and n 1 and n 2 are the indices of refraction , n = 1 in a vacuum and n > 1 in a transparent substance . When a beam of light crosses

900-442: A trance music production duo The Light (Glass) , a 1987 symphonic composition by Philip Glass The Light (Afrika Bambaataa album) , 1988 The Light (BGYO album) , 2021 The Light (Spock's Beard album) , 1995 "The Light" (BGYO song) , 2021 "The Light" (Common song) , 2000 "The Light" (Disturbed song) , 2015 "The Light" (Juice Wrld song) , 2023 "The Light" (Spock's Beard song) , 1995 The Light ,

960-557: A value of 298 000 000  m/s in 1862. Albert A. Michelson conducted experiments on the speed of light from 1877 until his death in 1931. He refined Foucault's methods in 1926 using improved rotating mirrors to measure the time it took light to make a round trip from Mount Wilson to Mount San Antonio in California. The precise measurements yielded a speed of 299 796 000  m/s . The effective velocity of light in various transparent substances containing ordinary matter ,

1020-530: Is also affected by the colour spectrum of light, a process known as photomorphogenesis . The speed of light in vacuum is defined to be exactly 299 792 458  m/s (approximately 186,282 miles per second). The fixed value of the speed of light in SI units results from the fact that the metre is now defined in terms of the speed of light. All forms of electromagnetic radiation move at exactly this same speed in vacuum. Different physicists have attempted to measure

1080-459: Is an active area of research. At larger scales, light pressure can cause asteroids to spin faster, acting on their irregular shapes as on the vanes of a windmill .   The possibility of making solar sails that would accelerate spaceships in space is also under investigation. Although the motion of the Crookes radiometer was originally attributed to light pressure, this interpretation

1140-429: Is caused by the surface roughness of the reflecting surfaces, and internal scatterance is caused by the difference of refractive index between the particles and medium inside the object. Like transparent objects, translucent objects allow light to transmit through, but translucent objects also scatter certain wavelength of light via internal scatterance. Refraction is the bending of light rays when passing through

1200-470: Is classified by wavelength into radio waves , microwaves , infrared , the visible spectrum that we perceive as light, ultraviolet , X-rays and gamma rays . The designation " radiation " excludes static electric , magnetic and near fields . The behavior of EMR depends on its wavelength. Higher frequencies have shorter wavelengths and lower frequencies have longer wavelengths. When EMR interacts with single atoms and molecules, its behavior depends on

1260-462: Is incorrect; the characteristic Crookes rotation is the result of a partial vacuum. This should not be confused with the Nichols radiometer , in which the (slight) motion caused by torque (though not enough for full rotation against friction) is directly caused by light pressure. As a consequence of light pressure, Einstein in 1909 predicted the existence of "radiation friction" which would oppose

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1320-654: Is less than in vacuum. For example, the speed of light in water is about 3/4 of that in vacuum. Two independent teams of physicists were said to bring light to a "complete standstill" by passing it through a Bose–Einstein condensate of the element rubidium , one team at Harvard University and the Rowland Institute for Science in Cambridge, Massachusetts and the other at the Harvard–Smithsonian Center for Astrophysics , also in Cambridge. However,

1380-449: Is regarded as the start of modern physical optics. Pierre Gassendi (1592–1655), an atomist, proposed a particle theory of light which was published posthumously in the 1660s. Isaac Newton studied Gassendi's work at an early age and preferred his view to Descartes's theory of the plenum . He stated in his Hypothesis of Light of 1675 that light was composed of corpuscles (particles of matter) which were emitted in all directions from

1440-504: The Académie des Sciences in 1817. Siméon Denis Poisson added to Fresnel's mathematical work to produce a convincing argument in favor of the wave theory, helping to overturn Newton's corpuscular theory. By the year 1821, Fresnel was able to show via mathematical methods that polarization could be explained by the wave theory of light if and only if light was entirely transverse, with no longitudinal vibration whatsoever. The weakness of

1500-428: The aurora borealis offer many clues as to the nature of light. A transparent object allows light to transmit or pass through. Conversely, an opaque object does not allow light to transmit through and instead reflecting or absorbing the light it receives. Most objects do not reflect or transmit light specularly and to some degree scatters the incoming light, which is called glossiness . Surface scatterance

1560-436: The human eye . Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 terahertz . The visible band sits adjacent to the infrared (with longer wavelengths and lower frequencies) and the ultraviolet (with shorter wavelengths and higher frequencies), called collectively optical radiation . In physics ,

1620-577: The quanta of electromagnetic field, and can be analyzed as both waves and particles . The study of light, known as optics , is an important research area in modern physics . The main source of natural light on Earth is the Sun . Historically, another important source of light for humans has been fire , from ancient campfires to modern kerosene lamps . With the development of electric lights and power systems , electric lighting has effectively replaced firelight. Generally, electromagnetic radiation (EMR)

1680-431: The reflection of light, but could only explain refraction by incorrectly assuming that light accelerated upon entering a denser medium because the gravitational pull was greater. Newton published the final version of his theory in his Opticks of 1704. His reputation helped the particle theory of light to hold sway during the eighteenth century. The particle theory of light led Pierre-Simon Laplace to argue that

1740-624: The refraction of light in his book Optics . In ancient India , the Hindu schools of Samkhya and Vaisheshika , from around the early centuries AD developed theories on light. According to the Samkhya school, light is one of the five fundamental "subtle" elements ( tanmatra ) out of which emerge the gross elements. The atomicity of these elements is not specifically mentioned and it appears that they were actually taken to be continuous. The Vishnu Purana refers to sunlight as "the seven rays of

1800-523: The Light , English rock band Other [ edit ] The Light (short story) , 1957 story by Poul Anderson "The Light" (Stargate SG-1) , an episode in the science fiction series Stargate SG-1 The Light (Leeds) , a shopping and leisure complex on The Headrow in Leeds City Centre, Leeds, England The Light (newspaper) , a British conspiracy newspaper The Light Waterfront ,

1860-456: The amount of energy per quantum it carries. EMR in the visible light region consists of quanta (called photons ) that are at the lower end of the energies that are capable of causing electronic excitation within molecules, which leads to changes in the bonding or chemistry of the molecule. At the lower end of the visible light spectrum, EMR becomes invisible to humans (infrared) because its photons no longer have enough individual energy to cause

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1920-470: The apparent size of images. Magnifying glasses , spectacles , contact lenses , microscopes and refracting telescopes are all examples of this manipulation. There are many sources of light. A body at a given temperature emits a characteristic spectrum of black-body radiation . A simple thermal source is sunlight , the radiation emitted by the chromosphere of the Sun at around 6,000  K (5,730  °C ; 10,340  °F ). Solar radiation peaks in

1980-605: The beam from the eye travels infinitely fast this is not a problem. In 55 BC, Lucretius , a Roman who carried on the ideas of earlier Greek atomists , wrote that "The light & heat of the sun; these are composed of minute atoms which, when they are shoved off, lose no time in shooting right across the interspace of air in the direction imparted by the shove." (from On the nature of the Universe ). Despite being similar to later particle theories, Lucretius's views were not generally accepted. Ptolemy (c. second century) wrote about

2040-452: The boundary between a vacuum and another medium, or between two different media, the wavelength of the light changes, but the frequency remains constant. If the beam of light is not orthogonal (or rather normal) to the boundary, the change in wavelength results in a change in the direction of the beam. This change of direction is known as refraction . The refractive quality of lenses is frequently used to manipulate light in order to change

2100-592: The concept of light is intended to include very-high-energy photons (gamma rays), additional generation mechanisms include: Light is measured with two main alternative sets of units: radiometry consists of measurements of light power at all wavelengths, while photometry measures light with wavelength weighted with respect to a standardized model of human brightness perception. Photometry is useful, for example, to quantify Illumination (lighting) intended for human use. The photometry units are different from most systems of physical units in that they take into account how

2160-503: The diameter of Earth's orbit. However, its size was not known at that time. If Rømer had known the diameter of the Earth's orbit, he would have calculated a speed of 227 000 000  m/s . Another more accurate measurement of the speed of light was performed in Europe by Hippolyte Fizeau in 1849. Fizeau directed a beam of light at a mirror several kilometers away. A rotating cog wheel

2220-497: The eye. Another supporter of the wave theory was Leonhard Euler . He argued in Nova theoria lucis et colorum (1746) that diffraction could more easily be explained by a wave theory. In 1816 André-Marie Ampère gave Augustin-Jean Fresnel an idea that the polarization of light can be explained by the wave theory if light were a transverse wave . Later, Fresnel independently worked out his own wave theory of light and presented it to

2280-434: The eyes and rays from a source such as the sun. In about 300 BC, Euclid wrote Optica , in which he studied the properties of light. Euclid postulated that light travelled in straight lines and he described the laws of reflection and studied them mathematically. He questioned that sight is the result of a beam from the eye, for he asks how one sees the stars immediately, if one closes one's eyes, then opens them at night. If

2340-437: The fifth century BC, Empedocles postulated that everything was composed of four elements ; fire, air, earth and water. He believed that goddess Aphrodite made the human eye out of the four elements and that she lit the fire in the eye which shone out from the eye making sight possible. If this were true, then one could see during the night just as well as during the day, so Empedocles postulated an interaction between rays from

2400-425: The force of pressure acting on the back. Hence, as the resultant of the two forces, there remains a force that counteracts the motion of the plate and that increases with the velocity of the plate. We will call this resultant 'radiation friction' in brief." Usually light momentum is aligned with its direction of motion. However, for example in evanescent waves momentum is transverse to direction of propagation. In

2460-421: The human eye responds to light. The cone cells in the human eye are of three types which respond differently across the visible spectrum and the cumulative response peaks at a wavelength of around 555 nm. Therefore, two sources of light which produce the same intensity (W/m ) of visible light do not necessarily appear equally bright. The photometry units are designed to take this into account and therefore are

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2520-418: The infrared and only a fraction in the visible spectrum. The peak of the black-body spectrum is in the deep infrared, at about 10 micrometre wavelength, for relatively cool objects like human beings. As the temperature increases, the peak shifts to shorter wavelengths, producing first a red glow, then a white one and finally a blue-white colour as the peak moves out of the visible part of the spectrum and into

2580-401: The infrared radiation. EMR in this range causes molecular vibration and heating effects, which is how these animals detect it. Above the range of visible light, ultraviolet light becomes invisible to humans, mostly because it is absorbed by the cornea below 360 nm and the internal lens below 400 nm. Furthermore, the rods and cones located in the retina of the human eye cannot detect

2640-433: The intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=The_Light&oldid=1218512952 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Light Light , visible light , or visible radiation is electromagnetic radiation that can be perceived by

2700-426: The luminous body, rejecting the "forms" of Ibn al-Haytham and Witelo as well as the "species" of Roger Bacon , Robert Grosseteste and Johannes Kepler . In 1637 he published a theory of the refraction of light that assumed, incorrectly, that light travelled faster in a denser medium than in a less dense medium. Descartes arrived at this conclusion by analogy with the behaviour of sound waves. Although Descartes

2760-413: The movement of matter. He wrote, "radiation will exert pressure on both sides of the plate. The forces of pressure exerted on the two sides are equal if the plate is at rest. However, if it is in motion, more radiation will be reflected on the surface that is ahead during the motion (front surface) than on the back surface. The backwardacting force of pressure exerted on the front surface is thus larger than

2820-510: The opposite. At that time, the speed of light could not be measured accurately enough to decide which theory was correct. The first to make a sufficiently accurate measurement was Léon Foucault , in 1850. His result supported the wave theory, and the classical particle theory was finally abandoned (only to partly re-emerge in the twentieth century as photons in quantum theory ). The %27Lights Its time-slot expanded from 7-9 AM to 6-9 AM Eastern Time during its short run. The program

2880-436: The popular description of light being "stopped" in these experiments refers only to light being stored in the excited states of atoms, then re-emitted at an arbitrary later time, as stimulated by a second laser pulse. During the time it had "stopped", it had ceased to be light. The study of light and the interaction of light and matter is termed optics . The observation and study of optical phenomena such as rainbows and

2940-601: The spectrum of each atom. Emission can be spontaneous , as in light-emitting diodes , gas discharge lamps (such as neon lamps and neon signs , mercury-vapor lamps , etc.) and flames (light from the hot gas itself—so, for example, sodium in a gas flame emits characteristic yellow light). Emission can also be stimulated , as in a laser or a microwave maser . Deceleration of a free charged particle, such as an electron , can produce visible radiation: cyclotron radiation , synchrotron radiation and bremsstrahlung radiation are all examples of this. Particles moving through

3000-435: The speed of light throughout history. Galileo attempted to measure the speed of light in the seventeenth century. An early experiment to measure the speed of light was conducted by Ole Rømer , a Danish physicist, in 1676. Using a telescope , Rømer observed the motions of Jupiter and one of its moons , Io . Noting discrepancies in the apparent period of Io's orbit, he calculated that light takes about 22 minutes to traverse

3060-406: The sun". The Indian Buddhists , such as Dignāga in the fifth century and Dharmakirti in the seventh century, developed a type of atomism that is a philosophy about reality being composed of atomic entities that are momentary flashes of light or energy. They viewed light as being an atomic entity equivalent to energy. René Descartes (1596–1650) held that light was a mechanical property of

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3120-562: The term "light" may refer more broadly to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays , X-rays , microwaves and radio waves are also light. The primary properties of light are intensity , propagation direction, frequency or wavelength spectrum , and polarization . Its speed in vacuum , 299 792 458  m/s , is one of the fundamental constants of nature. Like all types of electromagnetic radiation, visible light propagates by massless elementary particles called photons that represents

3180-486: The ultraviolet. These colours can be seen when metal is heated to "red hot" or "white hot". Blue-white thermal emission is not often seen, except in stars (the commonly seen pure-blue colour in a gas flame or a welder 's torch is in fact due to molecular emission, notably by CH radicals emitting a wavelength band around 425 nm and is not seen in stars or pure thermal radiation). Atoms emit and absorb light at characteristic energies. This produces " emission lines " in

3240-624: The very short (below 360 nm) ultraviolet wavelengths and are in fact damaged by ultraviolet. Many animals with eyes that do not require lenses (such as insects and shrimp) are able to detect ultraviolet, by quantum photon-absorption mechanisms, in much the same chemical way that humans detect visible light. Various sources define visible light as narrowly as 420–680 nm to as broadly as 380–800 nm. Under ideal laboratory conditions, people can see infrared up to at least 1,050 nm; children and young adults may perceive ultraviolet wavelengths down to about 310–313 nm. Plant growth

3300-427: The visible region of the electromagnetic spectrum when plotted in wavelength units, and roughly 44% of the radiation that reaches the ground is visible. Another example is incandescent light bulbs , which emit only around 10% of their energy as visible light and the remainder as infrared. A common thermal light source in history is the glowing solid particles in flames , but these also emit most of their radiation in

3360-480: The wave theory was that light waves, like sound waves, would need a medium for transmission. The existence of the hypothetical substance luminiferous aether proposed by Huygens in 1678 was cast into strong doubt in the late nineteenth century by the Michelson–Morley experiment . Newton's corpuscular theory implied that light would travel faster in a denser medium, while the wave theory of Huygens and others implied

3420-576: Was emitted in all directions as a series of waves in a medium called the luminiferous aether . As waves are not affected by gravity, it was assumed that they slowed down upon entering a denser medium. The wave theory predicted that light waves could interfere with each other like sound waves (as noted around 1800 by Thomas Young ). Young showed by means of a diffraction experiment that light behaved as waves. He also proposed that different colours were caused by different wavelengths of light and explained colour vision in terms of three-coloured receptors in

3480-432: Was for the first time qualitatively explained by Newton using the particle theory. Étienne-Louis Malus in 1810 created a mathematical particle theory of polarization. Jean-Baptiste Biot in 1812 showed that this theory explained all known phenomena of light polarization. At that time the polarization was considered as the proof of the particle theory. To explain the origin of colours , Robert Hooke (1635–1703) developed

3540-404: Was incorrect about the relative speeds, he was correct in assuming that light behaved like a wave and in concluding that refraction could be explained by the speed of light in different media. Descartes is not the first to use the mechanical analogies but because he clearly asserts that light is only a mechanical property of the luminous body and the transmitting medium, Descartes's theory of light

3600-521: Was placed in the path of the light beam as it traveled from the source, to the mirror and then returned to its origin. Fizeau found that at a certain rate of rotation, the beam would pass through one gap in the wheel on the way out and the next gap on the way back. Knowing the distance to the mirror, the number of teeth on the wheel and the rate of rotation, Fizeau was able to calculate the speed of light as 313 000 000  m/s . Léon Foucault carried out an experiment which used rotating mirrors to obtain

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