A report on Light

A triangular prism dispersing a beam of white light. The longer wavelengths (red) and the shorter wavelengths (blue) are separated.
The electromagnetic spectrum, with the visible portion highlighted
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Beam of sun light inside the cavity of Rocca ill'Abissu at Fondachelli-Fantina, Sicily
Due to refraction, the straw dipped in water appears bent and the ruler scale compressed when viewed from a shallow angle.
Hong Kong illuminated by colourful artificial lighting.
Pierre Gassendi.
Christiaan Huygens.
Thomas Young's sketch of a double-slit experiment showing diffraction. Young's experiments supported the theory that light consists of waves.
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Electromagnetic radiation within the portion of the electromagnetic spectrum that is perceived by the human eye.

- Light
A triangular prism dispersing a beam of white light. The longer wavelengths (red) and the shorter wavelengths (blue) are separated.

81 related topics with Alpha

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A modern pair of glasses

Glasses

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Glasses, also known as eyeglasses or spectacles, are vision eyewear, with lenses (clear or tinted) mounted in a frame that holds them in front of a person's eyes, typically utilizing a bridge over the nose and hinged arms (known as temples or temple pieces) that rest over the ears.

Glasses, also known as eyeglasses or spectacles, are vision eyewear, with lenses (clear or tinted) mounted in a frame that holds them in front of a person's eyes, typically utilizing a bridge over the nose and hinged arms (known as temples or temple pieces) that rest over the ears.

A modern pair of glasses
A skyline seen through a corrective lens, showing the effect of refraction
Safety glasses with side shields
Woman wearing sunglasses
Doubleframe eyewear with one set of lenses on the moving frame and another pair of lenses on a fixed frame (optional).
Glasses, c. 1920s, with springy cable temples
Modern glasses with a rectangular lens shape
Detail of a portrait of the Dominican Cardinal and renowned biblical scholar Hugh of Saint-Cher painted by Tommaso da Modena in 1352
Portrait of cardinal Fernando Niño de Guevara by El Greco circa 1600 shows glasses with temples passing over and beyond the ears
The Glasses Apostle by Conrad von Soest (1403)
Seated apostle holding lenses in position for reading. Detail from Death of the Virgin, by the Master of Heiligenkreuz, c. 1400–1430 (Getty Center).
French Empire gilt scissors glasses (with one lens missing), c. 1805
A portrait of Francisco de Quevedo y Villegas, 1580–1645
Harry S. Truman, 33rd President of the United States, had poor vision.
Woman wearing eyewear with non-prescription lenses in a fashion photo shoot.
Glasses - Decoration, Presi HQ, Budapest
Former United States senator Barry Goldwater in horn-rimmed glasses

Sunglasses provide more comfort and protection against bright light and often against ultraviolet (UV) light.

The 100-inch (2.54 m) Hooker reflecting telescope at Mount Wilson Observatory near Los Angeles, USA, used by Edwin Hubble to measure galaxy redshifts and discover the general expansion of the universe.

Telescope

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Optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation.

Optical instrument using lenses, curved mirrors, or a combination of both to observe distant objects, or various devices used to observe distant objects by their emission, absorption, or reflection of electromagnetic radiation.

The 100-inch (2.54 m) Hooker reflecting telescope at Mount Wilson Observatory near Los Angeles, USA, used by Edwin Hubble to measure galaxy redshifts and discover the general expansion of the universe.
17th century telescope
The 60-inch Hale (debuted in 1908) considered to be the first modern large research reflecting telescope.
The primary mirror assembly of James Webb Space Telescope under construction. This is a segmented mirror and its coated with Gold to reflect (orange-red) visible light, through near-infrared to the mid-infrared
Modern telescopes typically use CCDs instead of film for recording images. This is the sensor array in the Kepler spacecraft.
A 1.2-meter (47 in) reflecting telescope
Binoculars
The Very Large Array at Socorro, New Mexico, United States.
Einstein Observatory was a space-based focusing optical X-ray telescope from 1978.
The Compton Gamma Ray Observatory is released into orbit by the Space Shutte in 1991, and it would operate until the year 2000
The reflectors of HEGRA detect flashes of light in the atmosphere, thus detecting high energy particles
Equatorial-mounted Keplerian telescope
A diagram of the electromagnetic spectrum with the Earth's atmospheric transmittance (or opacity) and the types of telescopes used to image parts of the spectrum.
Six views of the Crab nebula supernova remnant, viewed at different wavelengths of light by various telescopes
The Five-hundred-meter Aperture Spherical radio Telescope in Guizhou, China, is the world's largest filled-aperture radio telescope

Optical telescopes, using visible light

Flying and glowing firefly, Photinus pyralis

Bioluminescence

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Flying and glowing firefly, Photinus pyralis
Female glowworm, Lampyris noctiluca
Male and female of the species Lampyris noctiluca mating. The female of this species is a larviform and has no wings, unlike the male.
Osamu Shimomura isolated the photoprotein aequorin and its cofactor coelenterazine from the crystal jelly Aequorea victoria in 1961.
Protein structure of the luciferase of the firefly Photinus pyralis. The enzyme is a much larger molecule than luciferin.
Coelenterazine is a luciferin found in many different marine phyla from comb jellies to vertebrates. Like all luciferins, it is oxidised to produce light.
Mycena chlorophos, a bioluminescent mushroom
Principle of counterillumination camouflage in firefly squid, Watasenia scintillans. When seen from below by a predator, the bioluminescence helps to match the squid's brightness and color to the sea surface above.
Stauroteuthis syrtensis bioluminescent photophores
Acanthephyra purpurea has photophores along its body which it uses in defense against predators.
Pyrosoma, a colonial tunicate; each individual zooid in the colony flashes a blue-green light.
A deep sea anglerfish, Bufoceratias wedli, showing the esca (lure)
Flashing of photophores of black dragonfish, Malacosteus niger, showing red fluorescence

Bioluminescence is the production and emission of light by living organisms.

A 175-watt mercury-vapor light approximately 15 seconds after starting.

Mercury-vapor lamp

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A 175-watt mercury-vapor light approximately 15 seconds after starting.
A closeup of a 175-W mercury vapor lamp. The small diagonal cylinder at the bottom of the arc tube is a resistor which supplies current to the starter electrode.
Cooper Hewitt lamp, 1903
Production of high-pressure mercury vapor lamps, 1965
Mercury vapor street light
Closeup after dark
Example of a phosphor-coated 125 W lamp
Line spectrum of mercury vapor. The blue-green tint of mercury vapor lamps is caused by the strong violet and green lines.
Low-pressure Hg lamps can be rather small, but efficient sources of deep UV light.

A mercury-vapor lamp is a gas-discharge lamp that uses an electric arc through vaporized mercury to produce light.

A photodetector salvaged from a CD-ROM drive. The photodetector contains three photodiodes, visible in the photo (in center).

Photodetector

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A photodetector salvaged from a CD-ROM drive. The photodetector contains three photodiodes, visible in the photo (in center).
A commercial amplified photodetector for use in optics research

Photodetectors, also called photosensors, are sensors of light or other electromagnetic radiation.

Photograph by Bertall & Cie

Léon Foucault

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French physicist best known for his demonstration of the Foucault pendulum, a device demonstrating the effect of Earth's rotation.

French physicist best known for his demonstration of the Foucault pendulum, a device demonstrating the effect of Earth's rotation.

Photograph by Bertall & Cie
Diagram of a variant of Foucault's speed of light experiment where a modern laser is the source of light
Grave of Jean Bernard Léon Foucault in Montmartre Cemetery

With Hippolyte Fizeau he carried out a series of investigations on the intensity of the light of the sun, as compared with that of carbon in the arc lamp, and of lime in the flame of the oxyhydrogen blowpipe; on the interference of infrared radiation, and of light rays differing greatly in lengths of path; and on the chromatic polarization of light.

The emission of electrons from a metal plate caused by light quanta – photons.

Photoelectric effect

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The emission of electrons from a metal plate caused by light quanta – photons.
Schematic of the experiment to demonstrate the photoelectric effect. Filtered, monochromatic light of a certain wavelength strikes the emitting electrode (E) inside a vacuum tube. The collector electrode (C) is biased to a voltage VC that can be set to attract the emitted electrons, when positive, or prevent any of them from reaching the collector when negative.
Diagram of the maximum kinetic energy as a function of the frequency of light on zinc.
The gold leaf electroscope to demonstrate the photoelectric effect. When the electroscope is negatively charged, there is an excess of electrons and the leaves are separated. If short wavelength, high-frequency light (such as ultraviolet light obtained from an arc lamp, or by burning magnesium, or by using an induction coil between zinc or cadmium terminals to produce sparking) shines on the cap, the electroscope discharges, and the leaves fall limp. If, however, the frequency of the light waves is below the threshold value for the cap, the leaves will not discharge, no matter how long one shines the light at the cap.
Photomultiplier
Angle-resolved photoemission spectroscopy (ARPES) experiment. Helium discharge lamp shines ultraviolet light onto the sample in ultra-high vacuum. Hemispherical electron analyzer measures the distribution of ejected electrons with respect to energy and momentum.

The photoelectric effect is the emission of electrons when electromagnetic radiation, such as light, hits a material.

Radiometry

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Radiometry is a set of techniques for measuring electromagnetic radiation, including visible light.

A polygon and its two normal vectors

Normal (geometry)

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Object such as a line, ray, or vector that is perpendicular to a given object.

Object such as a line, ray, or vector that is perpendicular to a given object.

A polygon and its two normal vectors
A normal to a surface at a point is the same as a normal to the tangent plane to the surface at the same point.
A curved surface showing the unit normal vectors (blue arrows) to the surface
A vector field of normals to a surface
Diagram of specular reflection

The normal is often used in 3D computer graphics (notice the singular, as only one normal will be defined) to determine a surface's orientation toward a light source for flat shading, or the orientation of each of the surface's corners (vertices) to mimic a curved surface with Phong shading.

A 200 mm refracting telescope at the Poznań Observatory

Refracting telescope

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Type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope).

Type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope).

A 200 mm refracting telescope at the Poznań Observatory
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Optical diagram of Galilean telescope
y – Distant object; y′ – Real image from objective; y″ – Magnified virtual image from eyepiece;
D – Entrance pupil diameter; d – Virtual exit pupil diameter;  L1 – Objective lens;  L2 – Eyepiece lens e – Virtual exit pupil – Telescope equals
Engraved illustration of a 150 ft focal length Keplerian astronomical refracting telescope built by Johannes Hevelius.
Alvan Clark polishes the big Yerkes achromatic objective lens, over 1 meter across, in 1896.
This 12 inch refractor is mounted in dome and a mount the rotates with the turn of the Earth
The Greenwich 28-inch refractor is a popular tourist attraction in 21st century London
The Apochromatic lens usually comprises three elements that bring light of three different frequencies to a common focus
The 102 cm refractor, at Yerkes Observatory, the largest achromatic refractor ever put into astronomical use (photo taken on 6 May 1921, as Einstein was visiting)
The "Große Refraktor" a double telescope with a 80cm (31.5") and 50 cm (19.5") lenses, was used to discover calcium as an interstellar medium in 1904.
Astronaut trains with camera with large lens
Touristic telescope pointed to Matterhorn in Switzerland
The Yerkes Great refractor mounted at the 1893 World's Fair in Chicago; the tallest, longest, and biggest aperture refactor up to that time.
The 68 cm refractor at the Vienna University Observatory

The objective in a refracting telescope refracts or bends light.