Light

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Exploring the Science of Light! (Optical Society of America)

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light : electromagnetic radiation of any wavelength that travels in a vacuum with a speed of 299,792,458 meters (about 186,000 miles) per second; specifically : such radiation that is visible to the human eye. — Webster

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Encyclopedia

Light is electromagnetic radiation within a certain portion of the electromagnetic spectrum. The word usually refers to visible light, which is the visible spectrum that is visible to the human eye and is responsible for the sense of sight. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), or 4.00 × 10−7 to 7.00 × 10−7 m, between the infrared (with longer wavelengths) and the ultraviolet (with shorter wavelengths). This wavelength means a frequency range of roughly 430–750 terahertz (THz).

The main source of light on Earth is the Sun. Sunlight provides the energy that green plants use to create sugars mostly in the form of starches, which release energy into the living things that digest them. This process of photosynthesis provides virtually all the energy used by living things. 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. Some species of animals generate their own light, a process called bioluminescence. For example, fireflies use light to locate mates, and vampire squids use it to hide themselves from prey.

The primary properties of visible light are intensity, propagation direction, frequency or wavelength spectrum, and polarization, while its speed in a vacuum, 299,792,458 metres 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 a vacuum.

In physics, the term light sometimes refers to electromagnetic radiation of any wavelength, whether visible or not. In this sense, gamma rays, X-rays, microwaves and radio waves are also light. Like all types of electromagnetic radiation, visible light propagates as waves. However, the energy imparted by the waves is absorbed at single locations the way particles are absorbed. The absorbed energy of the EM waves is called a photon, and represents the quanta of light. When a wave of light is transformed and absorbed as a photon, the energy of the wave instantly collapses to a single location, and this location is where the photon “arrives.” This is what is called the wave function collapse. This dual wave-like and particle-like nature of light is known as the wave–particle duality. The study of light, known as optics, is an important research area in modern physics. — Wikipedia

Optics (Eric Weisstein’s World of Physics, Wolfram Research)
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Light (WolframAlpha), Optics (WolframAlpha)

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Optics is the branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation such as X-rays, microwaves, and radio waves exhibit similar properties.

Most optical phenomena can be accounted for using the classical electromagnetic description of light. Complete electromagnetic descriptions of light are, however, often difficult to apply in practice. Practical optics is usually done using simplified models. The most common of these, geometric optics, treats light as a collection of rays that travel in straight lines and bend when they pass through or reflect from surfaces. Physical optics is a more comprehensive model of light, which includes wave effects such as diffraction and interference that cannot be accounted for in geometric optics. Historically, the ray-based model of light was developed first, followed by the wave model of light. Progress in electromagnetic theory in the 19th century led to the discovery that light waves were in fact electromagnetic radiation.

Some phenomena depend on the fact that light has both wave-like and particle-like properties. Explanation of these effects requires quantum mechanics. When considering light’s particle-like properties, the light is modeled as a collection of particles called “photons”. Quantum optics deals with the application of quantum mechanics to optical systems.

Optical science is relevant to and studied in many related disciplines including astronomy, various engineering fields, photography, and medicine (particularly ophthalmology and optometry). Practical applications of optics are found in a variety of technologies and everyday objects, including mirrors, lenses, telescopes, microscopes, lasers, and fiber optics. — Wikipedia

Encyclopædia Britannica

Discovery

Scientists & Discovery, Light (Museum Victoria Australia)

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How Light Works (HowStuffWorks)

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History

Optics Timeline (Optical Society of America)
A History of Light and Lighting (Bill Williams)

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Quotations Page Bartlett’s

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The Museum of Optics (University of Arizona)

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WorldCat, Library of Congress, UPenn Online Books, Open Library

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OER Commons: Open Educational Resources

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Careers in Optics and Photonics (Optical Society of America)

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International Society for Optics and Phontonics (SPIE)
Optical Society of America

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International Society for Optics and Phontonics (SPIE)
Nature of Light (Science Daily)
Optics and Photonics News (Phys.org), Optics (Science 2.0), NPR Archives

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USA.gov

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We Are One Step Closer to a Lightsaber (Darren Orf, Popular Mechanics
Scientists Catch Up With Jedi in Understanding Light (Richard Adhikari, TechNewsWorld)

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OEDILF: The Omnificent English Dictionary In Limerick Form

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Optics.org News latest News from Optics.org


Optics News -- ScienceDaily Optics. Can light go backwards? Researchers push the limits of our understanding of light. Also see amazing new applications of light energy. Full-text, images, free.

  • Uncovering the secrets of ultra-low frequency...
    on October 18, 2021 at 3:25 pm

    New methods of detecting ultra-low frequency gravitational waves can be combined with other, less sensitive measurements to deliver fresh insights into the early development of our universe, according to researchers.

  • Scientists discover method to boost energy...
    on October 18, 2021 at 2:59 pm

    The variety of humble algae that cover the surface of ponds and seas could hold the key to boosting the efficiency of artificial photosynthesis, allowing scientists to produce more energy and lower waste in the process. A study showed how encasing algae protein in liquid droplets can dramatically enhance the algae's light-harvesting and energy-conversion properties by up to three times. This energy is produced as the algae undergoes photosynthesis, which is the process used by plants, algae and […]

  • Ultrafast magnetism: heating magnets, freezing...
    on October 15, 2021 at 10:42 pm

    Magnetic solids can be demagnetized quickly with a short laser pulse, and there are already so-called HAMR (Heat Assisted Magnetic Recording) memories on the market that function according to this principle. However, the microscopic mechanisms of ultrafast demagnetization remain unclear. Now, a team has developed a new method at BESSY II to quantify one of these mechanisms and applied it to the rare-earth element Gadolinium, whose magnetic properties are caused by electrons on both the 4f and […]

  • Intelligent optical chip to improve...
    on October 15, 2021 at 1:47 pm

    Scientists have developed a smart pulse-shaper integrated on a chip.

  • New metalens focuses light with ultra-deep holes
    on October 14, 2021 at 6:20 pm

    Researchers developed a metasurface that uses very deep, very narrow holes, rather than very tall pillars, to focus light to a single spot.


Optics & Photonics News - Optics, Photonics, Physics News The latest news on Optics and Photonics

  • The four LHC experiments are getting ready for...
    on October 18, 2021 at 4:06 pm

    Since 2019, many places at CERN have been operating like beehives to complete the scheduled upgrades for the second long shutdown (LS2) of the accelerator complex. This period of intense work is now coming to an end with the injection of the first pilot beams into the LHC. This major milestone will be featured during a live event on CERN's social media channels on 20 October at 4 pm (CEST).

  • Tuning transparency and opacity
    on October 18, 2021 at 12:06 pm

    Making a dark human hair transparent, or even an opaque bar of silicon: this optical "sorcery" is possible by manipulating the incident light. This new phenomenon is called "mutual extinction and transparency." Until now only existing in theory, photonics researchers of the University of Twente's MESA+ Institute demonstrated the effect with experiments. Applications include, for example, broadening the applicability of microscopy, as to include observation of opaque objects. The research team […]

  • Intelligent optical chip to improve...
    on October 15, 2021 at 2:47 pm

    From the internet, to fiber or satellite communications and medical diagnostics, our everyday life relies on optical technologies. These technologies use optical pulsed sources to transfer, retrieve or compute information. Gaining control over optical pulse shapes thus paves the way for further advances.

  • Ultrafast optical switching can save overwhelmed...
    on October 15, 2021 at 1:50 pm

    EPFL and Microsoft Research scientists demonstrated ultrafast optical circuit switching using a chip-based soliton comb laser and a completely passive diffraction grating device. This particular architecture could enable an energy-efficient optical datacenter to meet enormous data bandwidth requirements in future.

  • How to force photons to never bounce back
    on October 13, 2021 at 3:00 pm

    Topological insulators are materials whose structure forces photons and electrons to move only along the material's boundary and only in one direction. These particles experience little resistance and travel freely past obstacles such as impurities, fabrication defects, a change of signal's trajectory within a circuit, or objects placed intentionally in the particles' path. That's because these particles, instead of being reflected by the obstacle, go around it "like river-water flowing past a […]