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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Light (WolframAlpha), Optics (WolframAlpha)

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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)

Preservation

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.

  • Graphene-based wearables for health monitoring,...
    on February 16, 2019 at 12:25 am

    Scientists have developed dozens of new graphene-based prototypes. These technologies aim to turn mobile phones into life saving devices. […]

  • Shaping light lets 2D microscopes capture 4D data
    on February 14, 2019 at 8:31 pm

    Researchers have created a method to design custom masks that transform 2D fluorescent microscopy images into 3D movies. […]

  • Direct-write quantum calligraphy in monolayer...
    on February 14, 2019 at 4:55 pm

    An interdisciplinary team of researchers have developed a way to directly write quantum light sources, which emit a single photon of light at a time, into monolayer semiconductors. […]

  • High-speed surveillance in solar cells catches...
    on February 14, 2019 at 2:34 pm

    Using synchronized lasers pulses, researchers developed a new method of electrostatic force microscopy that can record movies with frames as fast as 300 nanoseconds. This is fast enough to watch electrons move inside solar cells, which can lead to more efficient solar power devices. […]

  • The first walking robot that moves without GPS
    on February 13, 2019 at 7:27 pm

    Desert ants are extraordinary solitary navigators. Researchers were inspired by these ants as they designed AntBot, the first walking robot that can explore its environment randomly and go home automatically, without GPS or mapping. This work opens up new strategies for navigation in autonomous vehicles and robotics. […]


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

  • Researchers discover anti-laser masquerading as...
    on February 15, 2019 at 4:10 pm

    Researchers at Duke University have discovered that a perfect absorber of electromagnetic waves they described in a 2017 paper can easily be tweaked into a sort of "time-reversed laser" known as a coherent perfect absorber (CPA). […]

  • After 90 years, a better way to measure the...
    on February 15, 2019 at 2:30 pm

    Researchers at the National Institute of Standards and Technology (NIST), in collaboration with the U.S. Government Publishing Office (GPO), have developed a novel, nondestructive method to rapidly measure the wood and non-wood fiber components in paper. […]

  • Shaping light lets 2-D microscopes capture 4-D...
    on February 14, 2019 at 7:11 pm

    Rice University researchers have added a new dimension to their breakthrough technique that expands the capabilities of standard laboratory microscopes. […]

  • High-speed surveillance in solar cells catches...
    on February 14, 2019 at 12:58 pm

    A research team at Osaka University has developed an improved method for producing microscope images that can spot speedy electrons zipping through nanomaterials used in solar panels. By applying laser light to the device at just the right times, this group achieved nanosecond time resolution for the first time while maintaining the magnification. This work could improve the quality of photovoltaic materials for devices such as solar panels by helping to identify and eliminate inefficiencies […]

  • Running an LED in reverse could cool future...
    on February 13, 2019 at 8:22 pm

    In a finding that runs counter to a common assumption in physics, researchers at the University of Michigan ran a light emitting diode (LED) with electrodes reversed in order to cool another device mere nanometers away. […]