Light

of these articles treats light as radiation, further meanings is under light (term clarifying)

the visible light is the range of the electromagnetic radiation, which of the human eye can be noticed, that is the electromagnetic waves within the range of approximately380 to 780 nanometers (Nm) wavelength. In physics the term light stands also for the entire electromagnetic wave spectrum.

Light
pours

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physiology

the different sensitivity of pigment - molecules (blue, green yellow, orange) in different Sehzapfenarten and Stäbchen of the human eye for different wavelengths (V (λ) - curve) is topic of the Fotometrie. While the Sehzapfen is responsible for the color seeing, the Sehstäbchen in the retina with the Retinal - molecules under Rhodopsin - registers splitting off luminous intensity.

The color effect of physiological seeing results from those Absorption of individual wavelengths by a coloring material. If certain wavelengths are absorbed, the color impression from the remaining wavelengths ( complementary color) develops. A green sheet absorbed therefore not in the wavelength coverage “green” separate within the complementary range “red” (680 Nm) and “blue” (430Nm). See for this chlorophyll.

The light occurring in the environment is a mixture of different wavelengths. By a diffraction grating or a prism one can divide this polychromatische (multi color) light into its monochromatic (in-colored) components. Everyone of these monochromatic light components correspondsa specific human color impression, the Spektralfarben in such a way specified or colors of the rainbow. In the order of increasing wavelength one finds:

Light 400-700 Nm reference: At the computer screen only an impression very limited by the chromatic spectrum of the light can be made (this picture), there to these onlythree basic colours and their overlays to represent knows. Particularly in the internmediate tones and with the transition to the infrared/ultraviolet the display technology pushes to its borders.

**Spektralfarben**
colour	wavelength	Wellenfrequenz	energy per photon
violet	380 - 420 Nm	789 - 714THz	3.26 - 2.95 eV
blue	420 - 490 Nm	714 - 612 THz	2.95 - 2.53 eV
green	490 - 575 Nm	612 - 522 THz	2.53 - 2.16 eV
yellow	575 - 585 Nm	522 - 513 THz	2,16 - 2.12 eV
orange	585 - 650 Nm	513 - 462 THz	2.12 - 1.91 eV
red	650 - 750 Nm	462 - 400 THz	1.91 - 1.65 eV

the transitions between colors are flowing, the personal color impression individualdesignatable countable colors is subjective and to language, tradition and thinking due. The words for colors, occurring in different languages (original), occupy this.

The individual color gamuts contain different in each case colours. So is the intermediate range between blue and green about alsoTo designate door gravel or cyanogen. Other noticed colors (for example brown) result in the case of light, in that several wavelengths occur (additives color blending) or by subtraktive color blending from filtered white light.

Electromagnetic radiation beyond the human border of the visibilitylower wavelength than violet up to a certain frequency than ultraviolet or UV-RADIATION , such is named with larger wavelength as red up to a certain wavelength than infrared radiation. The range of the visible light with animals yields partiallysubstantially from human seeing.

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physics

one of the main sources of the light is the sun. Artificial sources of light are for example lamps, fluorescent tubes, light emitting diodes, lasers and chemical light.

Light became (some years ago still) inexplaining model as wave or alternatively as river with a particle character described. This wave particle dualism of the light can be described however today in the context of quantum physics mathematically precisely.

Light particles are called also photons. They possess no proper mass and move in Vacuum always with speed of light (C).

The connection between this critical speed (C) in the vacuum and its energy level (E) is defined by the mass (m), according to the famous Einstein formula:

E = m · C ²

The connection between the frequency (f) and that light - energy (E), by the Planck quantum of action (h), which as it were for the particle character of the light stands, by the following formula one describes.

E = h ·f

Aufgrund der Massekorrelation unterliegt das Licht generell der Gravitation und wird im Gravitatonsfeld, bzw. in the area curved and/or. diverted. Even a weak gravitational field carries, e.g. for same reason in addition. in a ring laser to prove leaves. Throughlight can relativistic effects be so also braked and affected by gravitation.

If electrons of a higher energy level jump on a lower energy level in the atom, will emitted photons, these can by humans as light be noticed (luminescence). Usuallythe energy is delivered with back traps on the lower level however than kinetic energy or thermal energy (infrared radiation). With the Autotrophen organisms the freed amount of energy in chemical compounds is bound (see photosynthesis).

With organic coloring materials the delokalsierten can Pi electron systems by frequencies within the visible range on a higher level to be lifted. Thus depending upon molecule determined wavelengths are absorbed.

With inorganic coloring materials electrons become lively from the D orbitals of an atom into D-orbital lain energetically more highly (ligand field theory)or they change their position between Zentralion and ligand within a complex (load transfer complexes). See also: Complex chemistry.

Beside the wavelength and/or color light is still characterized by the coherency , interference and the polarization and further measurable parameters.

One calls completely translucent articles transparent (transparency). Limits translucent (not transparent) articles also as „opaque “or „opak “are designated. The degree the lights permeability is then the degree „of the opacity “. Nichtlichtdurchlässigkeit is called also obscure.

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light in the society

light is, like fires, one of the most important phenomena for all cultures. Artificially produced light from lamps makes nowadays a pleasant and safe life for humans possible also with terrestrial darkness (night) and in coveredAreas (caves, buildings). The function group, which produces light, becomes technical, when lamp marks. The owner for the lamp forms a light with this. Light and light are also synonyms for intelligence (consider light view) and leave its meaning forthe Sozialisation of individuals in the group recognize. A lack of intelligence is equated with mental darkness.

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light in the open air

light in the open air has an auxiliary function for terrestrial navigation (pedestrian, driver) with darkness, asoptical signal or for decoration - and advertising purposes. It ranks as an environmental factor among the immissions i.S. the federal immission control law (BImSchG) (Germany). Light immissions of lighting systems can disturb the living and sleep need of humans and animals substantially and also technicalProcesses obstruct. Are accordingly in the so-called. “Light guideline “ of the countries (Germany) yardsticks put for the evaluation (space) of the clarification and (psychological ) the glare firmly. Particularly disturbing intensively colored or flashing light can work. Those are responsible with complaints Environment - and/or. Immission control authorities of the countries (Germany). Negative effects concern the road safety (navigation at night, physiological glare z. B. by wrongly adjusted headlights or by surface lighting beside roads). Influences on the animal world (z. B. Tighten night-active insects,Disturbance of the bird flight with migratory birds) and the general clarification of the atmosphere (light contamination, z. B. impossible astronomical observation due to dispersion of the lamp light in the atmosphere of the night sky).

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proof

light can most simply with the eye provenbecome, or with different instruments by optical detectors, as photographic film or with special radiation detectors or sensors or indirect by chemical or biological processes like photosynthesis or photolysis or by physical procedures, like fluorescence or photo luminescence. Sensors contain usually semiconductor detectors, which convert light into electrical tension. Complex sensors (LINE array/ line sensors and matrix array/ surface sensors), which serve also in scanners and digital cameras as photograph element.

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sizes and units

photon
Speed of light
light-current (lumen)
quantity of light (lumen customer)
luminous intensity (candela)
brilliance (Candela/m ²)
density of light (lux)
photolithography (optics) (Newton customer)
color of light (Kelvin)
light-year

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literature

Albert Einstein: Over the production and conversion of the light heuristic criterion concerned. in: Annals of physics 1905, S. 132-148 (with this contribution Einstein the wave particle dualism of the light justified).
Klaus Hentschel: Einstein and the light quantum hypothesis. in: Scientific ones round-look.58.2005, 6, S. 311-319.ISSN 0028-1050
Thomas roll ago, harsh ore roll ago: What is light? From the classical optics to quantum optics. C.H.Beck, Munich 1999. ISBN 3-406-44722-8
Sidney Perkowitz: A short history of the light. The study of a Mysteriums. Outthe American one translates of Hainer Kober. German paperbacks publishing house, Munich 1998. ISBN 3-423-33020-1 (amerik. Expenditure for original New York 1996, ISBN 0-8050-3211-8)