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)
Encyclopædia Britannica

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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.

  • New discovery improves use of optical tweezers
    on December 13, 2018 at 4:21 pm

    This year's Nobel Prize in Physics, awarded for discoveries in laser physics, recognizes optical tweezers. Now researchers have developed a method that greatly simplifies and improves the use of optical tweezers. […]

  • An energy-efficient way to stay warm: Sew...
    on December 13, 2018 at 1:36 pm

    What if, instead of turning up the thermostat, you could warm up with high-tech, flexible patches sewn into your clothes -- while significantly reducing your electric bill and carbon footprint? Engineers have found a cost-effective way to make thin, durable heating patches by using intense pulses of light to fuse tiny silver wires with polyester. Their heating performance is nearly 70 percent higher than similar patches created by other researchers. […]

  • How unconventional metals behave, with an eye on...
    on December 12, 2018 at 9:01 pm

    By trapping atoms in a lattice of light, researchers explore how unconventional metals conduct electricity, with an eye toward understanding high-temperature superconductors. […]

  • Bose-Einstein condensates cannot currently detect...
    on December 12, 2018 at 6:50 pm

    The gravitational waves created in the depths of space indeed reach Earth. Their effects, however, are so small that they could only be observed so far using kilometer-long measurement facilities. Physicists therefore discuss whether Bose-Einstein condensates with their ordered quantum properties could also detect these waves. Astronomers have now looked at these suggestions and have soberly determined that such evidence is far beyond the reach of current methods. […]

  • Crashes increase when speed limits dip far below...
    on December 12, 2018 at 6:50 pm

    Speed limits set only five miles per hour below engineering recommendations produce a statistically significant decrease in total, fatal and injury crashes, and property-damage-only crashes, according to a group of researchers. […]


Optics & Photonics News - Optics, Photonics, Physics News Phys.org provides the latest news on Optics and Photonics

  • New discovery improves use of optical tweezers
    on December 13, 2018 at 3:17 pm

    This year's Nobel Prize in Physics, awarded for discoveries in laser physics, recognizes optical tweezers. Now researchers from the University of Gothenburg have developed a method that greatly simplifies and improves the use of optical tweezers. […]

  • Mobile device makes the detection of parasitic...
    on December 13, 2018 at 3:08 pm

    Parasitic infections affect hundreds of millions of people, posing a serious public health threat worldwide. For example, sleeping sickness and Chagas disease are neglected tropical diseases that are caused by the bloodborne Trypanosoma parasite. Historically given little attention, these devastating diseases affect people mainly in sub-Saharan Africa and South America, causing enormous socioeconomic burden. […]

  • Invention promises airport security screening...
    on December 13, 2018 at 3:00 pm

    A research team led by The Australian National University (ANU) has invented a device that could be developed into ultra-sensitive cameras for security screening which would not require people to queue at airports. […]

  • Networking goes quantum
    on December 13, 2018 at 1:00 pm

    A scientist involved in expanding quantum communication to a network of users, is continuing his work at the University of Bristol. […]

  • Researchers design technology that sees nerve...
    on December 13, 2018 at 7:09 am

    Researchers at Stanford University, Palo Alto, California, have created a noninvasive technology that detects when nerve cells fire based on changes in shape. The method could be used to observe nerve activity in light-accessible parts of the body, such as the eye, which would allow physicians to quantitatively monitor visual function at the cellular level. The study was published in the journal Light: Science and Applications. The work was funded by the National Eye Institute, part of the […]