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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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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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)

Preservation

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.

  • Towards an 'orrery' for quantum gauge theory
    on August 19, 2019 at 8:43 pm

    Physicists have developed a new approach to couple quantized gauge fields to ultracold matter. The method might be the basis for a versatile platform to tackle problems ranging from condensed-matter to high-energy physics.

  • New artificial compound eye could improve 3D...
    on August 19, 2019 at 5:21 pm

    A newly created biologically inspired compound eye is helping scientists understand how insects use their compound eyes to sense an object and its trajectory with such speed. The compound eye could also be used with a camera to create 3D location systems for robots, self-driving cars and unmanned aerial vehicles.

  • Spinning lightwaves on a one-way street
    on August 19, 2019 at 3:27 pm

    Researchers have created a quantum spin wave for light. This can be a carrier of information for future nanotechnologies but with a unique twist: they only flow in one direction.

  • Optic nerve stimulation to aid the blind
    on August 19, 2019 at 3:27 pm

    Scientists are investigating new ways to provide visual signals to the blind by directly stimulating the optic nerve. Their preliminary study uses a new type of neural electrode and provides distinct signals.

  • Materials that can revolutionize how light is...
    on August 19, 2019 at 3:27 pm

    Scientists have designed organic molecules capable of generating two excitons per photon of light, a process called singlet fission. The excitons can live for much longer than those generated from their inorganic counterparts, which leads to an amplification of electricity generated per photon that is absorbed by a solar cell.


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

  • New artificial compound eye could improve 3-D...
    on August 19, 2019 at 4:43 pm

    If you've ever tried to swat a fly, you know that insects react to movement extremely quickly. A newly created biologically inspired compound eye is helping scientists understand how insects use their compound eyes to sense an object and its trajectory with such speed. The compound eye could also be used with a camera to create 3-D location systems for robots, self-driving cars and unmanned aerial vehicles.

  • Wired for sound: A third wave emerges in...
    on August 19, 2019 at 3:00 pm

    Optical fibres are our global nervous system, transporting terabytes of data across the planet in the blink of an eye.

  • Researchers document a quantum spin wave for light
    on August 19, 2019 at 1:48 pm

    Researchers at Purdue University have created a quantum spin wave for light. This can be a carrier of information for future nanotechnologies but with a unique twist: they only flow in one direction.

  • A laser for penetrating waves
    on August 19, 2019 at 12:24 pm

    The Landau-level laser is an exciting concept for an unusual radiation source. It could efficiently generate so-called terahertz waves, which can be used to penetrate materials, with possible applications in data transmission. So far, however, nearly all attempts to make such a laser have failed. An international team of researchers has now taken an important step in the right direction: In the journal Nature Photonics, they describe a material that generates terahertz waves by simply applying […]

  • Expanded ion beams light new way for...
    on August 16, 2019 at 11:07 am

    A new type of lens is lighting the way for expanded uses of large ions and building blocks for new materials. The lens may also address one of the fundamental bottlenecks for generating bright ion beams.