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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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.

  • Quality of laser beam shaping can be enhanced at...
    on April 24, 2019 at 3:29 pm

    Researchers have developed a technique for improving accuracy of laser beam shaping and wavefront obtained by conventional methods with no additional cost by optimizing virtual phase grating. […]

  • Photoacoustic endoscopy could improve Crohn's...
    on April 24, 2019 at 3:29 pm

    A newly developed endoscope could give doctors a better view of intestinal changes caused by Crohn's disease. This additional information would help improve treatment of the painful and debilitating form of inflammatory bowel disease, which currently affects hundreds of thousands of US adults. […]

  • Nanosized container with photoswitches: Release...
    on April 24, 2019 at 2:22 pm

    Researchers have developed a nanosized container bearing photoswitches that takes up hydrophobic compounds of various size and shape in water and subsequently releases them quantitatively by non-invasive light stimulus. The installed switches allow reusing of the container after successful release of the cargo. The novel system represents a versatile platform for future developments in fields such as materials chemistry and biomedicine. […]

  • Energy-saving new LED phosphor
    on April 24, 2019 at 2:22 pm

    The human eye is particularly sensitive to green, but less sensitive to blue and red. Chemists have now developed a new red phosphor whose light is well perceived by the eye. This increases the light yield of white LEDs by around one-sixth, which can significantly improve the energy efficiency of lighting systems. […]

  • New way to 'see' objects accelerates the future...
    on April 23, 2019 at 6:55 pm

    Researchers have discovered a simple, cost-effective, and accurate new method for equipping self-driving cars with the tools needed to perceive 3D objects in their path. […]


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

  • Quality of laser beam shaping can be enhanced at...
    on April 24, 2019 at 1:57 pm

    Researchers from Osaka University have developed a technique for improving accuracy of laser beam shaping and wavefront obtained by conventional methods with no additional cost by optimizing virtual phase grating. The results of their research were published in Scientific Reports. […]

  • Nanocomponent is a quantum leap for Danish...
    on April 24, 2019 at 1:30 pm

    University of Copenhagen researchers have developed a nanocomponent that emits light particles carrying quantum information. Less than one-tenth the width of a human hair, the miniscule component makes it possible to scale up and could ultimately reach the capabilities required for a quantum computer or quantum internet. The research result puts Denmark at the head of the pack in the quantum race. […]

  • Study opens a new route to achieving invisibility...
    on April 23, 2019 at 12:47 pm

    A pair of researchers at Tokyo Institute of Technology (Tokyo Tech) describes a way of making a submicron-sized cylinder disappear without using any specialized coating. Their findings could enable invisibility of natural materials at optical frequency and eventually lead to a simpler way of enhancing optoelectronic devices, including sensing and communication technologies. […]

  • Light-based computer hardware that can compete...
    on April 22, 2019 at 2:10 pm

    A team of researchers at NTT Corporation has developed a way to use light-based computer hardware that allows it to to compete with silicon. In their paper published in the journal Nature Photonics, the group describes their research, the devices they created and how well they worked. […]

  • Tiny pinholes in thin film could pave the way for...
    on April 19, 2019 at 12:28 pm

    Researchers in Korea have designed an ultrathin display that can project dynamic, multi-colored, 3-D holographic images, according to a study published in Nature Communications. […]