Light

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Introduction1

Dictionary

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

OneLook, Free Dictionary, Wiktionary

Thesaurus

Roget’s II (Thesaurus.com), Merriam-Webster Thesaurus, Visuwords

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

Portal

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

Search

Light (WolframAlpha), Optics (WolframAlpha)

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Innovation

Science

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)

Technology

How Light Works (HowStuffWorks)

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Preservation

History

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

Quotation

Quotations Page Bartlett’s

Museum

The Museum of Optics (University of Arizona)

Library

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

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Participation

Education

Course

OER Commons: Open Educational Resources

Community

Occupation

Careers in Optics and Photonics (Optical Society of America)

Organization

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

News

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

Book

ISBNdb

Government

Document

USA.gov

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Expression

Fun

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

Poem

OEDILF: The Omnificent English Dictionary In Limerick Form

Music

Song Lyrics

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More News …

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.

  • Artificial material protects light states on...
    on December 2, 2021 at 7:15 pm

    Light not only plays a key role as an information carrier for optical computer chips, but also in particular for the next generation of quantum computers. Its lossless guidance around sharp corners on tiny chips and the precise control of its interaction with other light are the focus of research worldwide. Scientists have now demonstrated the spatial confinement of a light wave to a point smaller than the wavelength in a 'topological photonic crystal.'

  • Physicists exploit space and time symmetries to...
    on December 2, 2021 at 7:15 pm

    Physicists have developed a theory describing how space reflection and time reversal symmetries can be exploited, allowing for greater control of transport and correlations within quantum materials.

  • Light-powered soft robots could suck up oil spills
    on December 2, 2021 at 7:15 pm

    A floating, robotic film could be trained to hoover oil spills at sea or remove contaminants from drinking water.

  • Color-changing magnifying glass gives clear view...
    on December 2, 2021 at 7:14 pm

    By trapping light into tiny crevices of gold, researchers have coaxed molecules to convert invisible infrared into visible light, creating new low-cost detectors for sensing.

  • Two-photon microscope provides unprecedented...
    on December 2, 2021 at 5:30 pm

    Advancing our understanding of the human brain will require new insights into how neural circuitry works in mammals, including laboratory mice. These investigations require monitoring brain activity with a microscope that provides resolution high enough to see individual neurons and their neighbors.


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

  • Artificial material protects light states on...
    on December 3, 2021 at 2:45 pm

    Light not only plays a key role as an information carrier for optical computer chips, particularly for the next generation of quantum computers. Its lossless guidance around sharp corners on tiny chips and the precise control of its interaction with other light are the focus of research worldwide. Scientists at Paderborn University have now demonstrated the spatial confinement of a light wave to a point smaller than the wavelength in a topological photonic crystal. These are artificial […]

  • Researchers one step closer to optoacoustic...
    on December 3, 2021 at 2:10 pm

    Skoltech researchers and their colleagues have come one step closer to a working optoacoustic endoscopic probe—a device that could slip inside a blood vessel and analyze atherosclerotic plaques by shining laser light on them to make them wobble like a loudspeaker membrane and betray their chemical composition with an ultrasound signature. This could prove useful in robotized microsurgery and medical diagnostics. The study recently came out in ACS Photonics.

  • Molecular device turns infrared into visible light
    on December 2, 2021 at 7:49 pm

    Light is an electromagnetic wave: It consists of oscillating electric and magnetic fields propagating through space. Every wave is characterized by its frequency, which refers to the number of oscillations per second, measured in Hertz (Hz). Our eyes can detect frequencies between 400 and 750 trillion Hz (or terahertz, THz), which define the visible spectrum. Light sensors in cell phone cameras can detect frequencies down to 300 THz, while detectors used for internet connections through optical […]

  • Color-changing magnifying glass gives clear view...
    on December 2, 2021 at 7:00 pm

    Detecting light beyond the visible red range of our eyes is hard to do, because infrared light carries so little energy compared to ambient heat at room temperature. This obscures infrared light unless specialized detectors are chilled to very low temperatures, which is both expensive and energy-intensive.

  • Researchers develop a two-photon microscope that...
    on December 2, 2021 at 5:45 pm

    Advancing our understanding of the human brain will require new insights into how neural circuitry works in mammals, including laboratory mice. These investigations require monitoring brain activity with a microscope that provides resolution high enough to see individual neurons and their neighbors.

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Related

Here are links to pages about closely related subjects.

Knowledge Realm

Physical

“Fundamentals”
Law (Constant) Relativity
Force Gravity, Electromagnetism (Light, Color)
Matter (Microscope) Molecule, Atom (Periodic Table), Particle

“Space”
Universe (Astronomical Instrument)
Galaxy Milky Way, Andromeda
Planetary System Star, Brown Dwarf, Planet, Moon

Our Neighborhood
Solar System Sun
Terrestrial Planet Mercury, Venus, Earth (Moon), Mars
Asteroid Belt Ceres, Vesta
Jovian Planet Jupiter, Saturn, Uranus, Neptune
Trans-Neptunian Object
Kuiper Belt Pluto, Haumea, Makemake
Scattered Disc Eris, Sedna, Planet X
Oort Cloud Etc. Scholz’s Star
Small Body Comet, Centaur, Asteroid

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Notes

1.   The resources on this page are are organized by a classification scheme developed exclusively for Cosma.