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Physical Realm
Physical Laws (Constants) Relativity
Matter Molecule, Atom (Periodic Table), Particle
Force Gravity, Electromagnetism (Light, Color)


These are organized by a classification scheme developed exclusively for Cosma. More…



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


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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Roget’s II (, Merriam-Webster Thesaurus, Visuwords


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



Light (WolframAlpha), Optics (WolframAlpha)



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


Scientists & Discovery, Light (Museum Victoria Australia)


How Light Works (HowStuffWorks)



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


Quotations Page Bartlett’s


The Museum of Optics (University of Arizona)


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




OER Commons: Open Educational Resources



Careers in Optics and Photonics (Optical Society of America)


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


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







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


OEDILF: The Omnificent English Dictionary In Limerick Form


Song Lyrics


More… News latest News from

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.

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    on April 21, 2021 at 7:12 pm

    Researchers have captured an image showing the internal orbits, or spatial distribution, of particles in an exciton - a goal that had eluded scientists for almost a century.

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    Researchers have found out that ultrafast switches in material properties can be prompted by laser pulses -- and why. This knowledge may enable new transistor concepts.

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    on April 20, 2021 at 5:10 pm

    As artificial intelligence has attracted interest, researchers are focused on understanding how the brain accomplishes cognition so they can construct systems with general intelligence comparable to humans' intelligence. Researchers propose an approach to AI that focuses on integrating photonic components with superconducting electronics; using light for communication and complex electronic circuits for computation could enable artificial cognitive systems of scale and functionality beyond what […]

  • Boosting fiber optics communications with...
    on April 20, 2021 at 5:10 pm

    Fiber optic technology is the holy grail of high-speed, long-distance telecommunications. Still, with the continuing exponential growth of internet traffic, researchers are warning of a capacity crunch. Researchers show how quantum-enhanced receivers could play a critical role in addressing this challenge. The scientists developed a method to enhance receivers based on quantum physics properties to dramatically increase network performance while significantly reducing the error bit rate and […]

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

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    on April 22, 2021 at 5:02 pm

    Researchers at the Paul Scherrer Institute PSI have succeeded for the first time in looking inside materials using the method of transient grating spectroscopy with ultrafast X-rays at SwissFEL. The experiment at PSI is a milestone in observing processes in the world of atoms. The researchers are publishing their research results today in the journal Nature Photonics.

  • 'Stickiness' key to better diagnostics and...
    on April 22, 2021 at 5:01 pm

    The 'stickiness', or viscosity, of microscopic liquids can now be measured thousands of times faster than ever before, potentially leading to better understanding of living cells, disease diagnostics and pharmaceutical testing.

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    on April 22, 2021 at 12:30 pm

    Scientists from Lawrence Livermore National Laboratory (LLNL) and the Laboratory for Laser Energetics (LLE) are working to improve polar direct drive (PDD) neutron sources on the National Ignition Facility (NIF), the world's most energetic laser.

  • Lighting it up: Fast material manipulation...
    on April 21, 2021 at 7:00 pm

    Researchers from the Physical Chemistry Department of the Fritz Haber Institute and the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg have found out that ultrafast switches in material properties can be prompted by laser pulses—and why. This knowledge may enable new transistor concepts.

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    on April 21, 2021 at 4:07 pm

    True super-resolution imaging beyond the diffraction limit remains a major challenge for far-field Raman microscopy especially in biological applications. Harnessing Stimulated Raman Excited Fluorescence (SREF) as an ultrasensitive vibrational contrast, a team at Columbia University has recently invented a novel super-resolution vibrational microscopy. Their new method opens up super-resolution, nanometer-spectral-resolution multicolor vibrational imaging of biological systems.