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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

OneLook, Free Dictionary, Wiktionary, Urban Dictionary


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.

  • Supersymmetry-inspired microlaser arrays pave way...
    on May 5, 2021 at 6:55 pm

    Ring microlasers are eyed as potential light sources for photonic applications, but they first must be made more powerful. Combining multiple microlasers into an array solves only half of the problem, as this adds noisy 'modes' to the resulting laser light. Now, thanks to the math behind supersymmetry theory, engineers have achieved single-mode lasing from such an array. By calculating the necessary properties for 'superpartner' arrays, they can cancel out the unwanted extra modes.

  • Repurposing tabletop sensors to search for dark...
    on May 5, 2021 at 6:55 pm

    Researchers across the dark matter community that have begun to wonder if they are looking for the right type of dark matter. They have proposed a new way to look for the particles that might make up dark matter by repurposing existing tabletop sensor technology.

  • Stabilization of the borafluorene anion with...
    on May 5, 2021 at 5:05 pm

    The incorporation of boron into polycyclic aromatic hydrocarbon systems leads to interesting chromophoric and fluorescing materials for optoelectronics, including organic light-emitting diodes (OLEDS) and field-effect transistors, as well as polymer-based sensors. A research team has now introduced a new anionic organoborane compound. Synthesis of the borafluorene succeeded through the use of carbenes.

  • Detailed look at how charge transfer distorts a...
    on May 5, 2021 at 1:44 pm

    When light hits certain molecules, it dislodges electrons that then move from one location to another, creating areas of positive and negative charge. This 'charge transfer' is highly important in many areas of chemistry, photosynthesis and semiconductor devices and solar cells. A new study reveals how a molecule's structure changes as charge is redistributed, with some chemical bonds getting longer and some shorter, before finally relaxing back into its original state.

  • Thin, large-area device converts infrared light...
    on May 5, 2021 at 1:44 pm

    An infrared imager developed by engineers could be used to see through smog and fog; easily locate blood vessels on a patient; and see through silicon wafers to inspect the quality of electronic boards. It is also slim, compact and less costly to fabricate than similar technologies.

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

  • Thin, large-area device converts infrared light...
    on May 5, 2021 at 4:15 pm

    Seeing through smog and fog. Mapping out a person's blood vessels while monitoring heart rate at the same time—without touching the person's skin. Seeing through silicon wafers to inspect the quality and composition of electronic boards. These are just some of the capabilities of a new infrared imager developed by a team of researchers led by electrical engineers at the University of California San Diego.

  • Observation of antichiral edge states in a...
    on May 5, 2021 at 12:18 pm

    A modified Haldane lattice exhibits the intriguing phenomenon of antichiral edge states that propagate in the same direction on opposite edges and co-exist with bulk states. Using an electric circuit, researchers have successfully demonstrated antichiral edge states. By measuring voltage distributions in the circuit, the key features of the antichiral edge states have been verified experimentally for the first time, including their group velocities and ability to propagate consistently in a […]

  • Study demonstrates swarm of photons that...
    on May 5, 2021 at 8:02 am

    Spinning or rotating objects are commonplace, from toy tops, fidget spinners, and figure skaters to water circling a drain, tornadoes, and hurricanes.

  • Complex shapes of photons to boost future quantum...
    on May 4, 2021 at 2:52 pm

    As the digital revolution has now become mainstream, quantum computing and quantum communication are rising in the consciousness of the field. The enhanced measurement technologies enabled by quantum phenomena, and the possibility of scientific progress using new methods, are of particular interest to researchers around the world.

  • Laser light makes a comeback (literally)
    on May 4, 2021 at 11:33 am

    Straight-line constant-speed propagation in free space is a basic characteristic of light. In a recent study published in Communications Physics, researchers from Osaka University discovered the phenomenon of reciprocating propagation of laser pulse intensity in free space.