These are organized by a classification scheme developed exclusively for Cosma. More…
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
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 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
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on November 18, 2019 at 2:11 pm
Society honors 23 distinguished award recipients from wide field of light-based science and technology.
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on November 14, 2019 at 7:11 pm
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on November 14, 2019 at 10:11 am
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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.
Scientists show how perovskite solar cells can...
on November 18, 2019 at 3:08 pm
Scientists have developed a method to analyze which pairs of materials in next-generation perovskite solar cells will harvest the most energy.
Foam offers way to manipulate light
on November 18, 2019 at 2:41 pm
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Squid camouflage may lead to next gen of...
on November 16, 2019 at 12:03 am
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Researchers generate terahertz laser with...
on November 14, 2019 at 7:13 pm
Researchers have built a compact device, the size of a shoebox, that produces a terahertz laser whose frequency they can tune over a wide range. The device is built from commercial, off-the-shelf parts and is designed to generate terahertz waves by spinning up the energy of molecules in nitrous oxide, or, as it's more commonly known, laughing gas.
Physicists irreversibly split photons by freezing...
on November 14, 2019 at 7:12 pm
Light can be directed in different directions, usually also back the same way. Physicists have however succeeded in creating a new one-way street for light. They cool photons down to a Bose-Einstein condensate, which causes the light to collect in optical 'valleys' from which it can no longer return. The findings could also be of interest for the quantum communication of the future.
Optics & Photonics News - Optics, Photonics, Physics News Phys.org provides the latest news on Optics and Photonics
Quantum light improves sensitivity of biological...
on November 18, 2019 at 8:46 pm
In a new study, researchers showed that quantum light can be used to track enzyme reactions in real time. The work brings together quantum physics and biology in an important step toward the development of quantum sensors for biomedical applications.
Foam offers way to manipulate light
on November 18, 2019 at 1:54 pm
There is more to foam than meets the eye. Literally. A study by Princeton scientists has shown that a type of foam long studied by scientists is able to block particular wavelengths of light, a coveted property for next-generation information technology that uses light instead of electricity.
Researchers create better light-trapping devices
on November 18, 2019 at 1:07 pm
Anyone who's ever played the drums, tuned a guitar, or even made a wine glass "sing" by circling a finger along its edge knows about resonance. Acoustic resonators, like the cavity of a drum or a half-full wine glass, naturally vibrate at certain frequencies of sound waves to produce specific tones. The phenomenon of resonance can also be applied to light waves, with optical resonators being key components of devices such as lasers and sensors.
Hot electrons harvested without tricks
on November 15, 2019 at 7:00 pm
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Scientists develop near ambient pressure...
on November 15, 2019 at 3:11 pm
A research group led by Prof. Fu Qiang and Prof. Bao Xinhe at the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) have developed near ambient pressure photoemission electron microscopy (AP-PEEM) with a tunable deep-ultraviolet (DUV) laser source as the excitation source.