Light

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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. — Merriam-Webster See also OneLook

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). — Wikipedia

Light (Encyclopædia Britannica)

Search

Light (WolframAlpha)

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Inspiration

Inside Science (American Institute of Physics, YouTube Channel)
Inside Science (American Institute of Physics, Official Website)

The Illusions Index (Centre for the Study of Perceptual Experience, University of Glasgow)
Centre for the Study of Perceptual Experience (University of Glasgow)

152 Visual Phenomena & Optical Illusions with Explanations (Michael Bach)
Visual Phenomena & Optical Illusions Sources (Michael Bach)

Optical Illusions (Kevin Stone, BrainBashers)

Interactive Optical Illusions (Gary Fabjance Chicago Magicians)

Optical Illusions and How They Work (American Museum of National History)

Talks about Light (TED: Ideas Worth Spreading)
Articles about Light (Big Think)

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Innovation

Science

Optics is the branch of physics that studies 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. — Wikipedia

Optics (Encyclopædia Britannica)
Optics (Eric Weisstein’s World of Physics, Wolfram Research)
Optics (WolframAlpha)

Electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 1025 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus. This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end. The electromagnetic waves in each of these bands have different characteristics, such as how they are produced, how they interact with matter, and their practical applications. — Wikipedia

Spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Historically, spectroscopy originated as the study of the wavelength dependence of the absorption by gas phase matter of visible light dispersed by a prism. Spectroscopy, primarily in the electromagnetic spectrum, is a fundamental exploratory tool in the fields of physics, chemistry, and astronomy, allowing the composition, physical structure and electronic structure of matter to be investigated at the atomic, molecular and macro scale, and over astronomical distances. — Wikipedia

Molecules and Light (PHET Interactive Simulations, University of Colorado)

Spectroscopy (Encyclopædia Britannica)

Technology

Laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word “laser” is an acronym for light amplification by stimulated emission of radiation. A laser differs from other sources of light in that it emits light which is coherent. Spatial coherence allows a laser to be focused to a tight spot, enabling applications such as laser cutting and lithography. Spatial coherence also allows a laser beam to stay narrow over great distances (collimation), enabling applications such as laser pointers and lidar (light detection and ranging). Lasers can also have high temporal coherence, which allows them to emit light with a very narrow spectrum. Alternatively, temporal coherence can be used to produce ultrashort pulses of light with a broad spectrum but durations as short as a femtosecond. — Wikipedia

Laser (Encyclopædia Britannica)
Lasers (Eric Weisstein’s World of Physics, Wolfram Research)

Commerce

Entrepreneurship

Optics Campaigns (Kickstarter)

Product

Optics Gifts (Zazzle)

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Preservation

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Participation

International Day of Light, May 16 (UNESCO, United Nations)

Education

Science Trek (YouTube Channel)
Science Trek (Official Website)

Light and Color (Science Trek)

Optical Illusions (Exploring the Science of Light, Optical Society of America)
Exploring the Science of Light (Optical Society of America)

Optical Illusions (Optics 4 Kids)
What is Optics (Optics 4 Kids)

Light & Optics (Physics4Kids)

Light (Crash Course Astronomy)

Exploring the Science of Light! (Optical Society of America)
Explore the Electromagnetic Spectrum (Space Place, NASA)
Light & Radiation (PHET Interactive Simulations, University of Colorado)

MERLOT: Multimedia Educational Resource for Learning and Online Teaching
OER Commons: Open Educational Resources

Course

Optical Materials and Devices (MITx)
Spectroscopy (MIT OpenCourseWare)

Community

Occupation

Careers in Optics and Photonics (Optica)

Optometrists (CareerOneStop, U.S. Department of Labor, Employment and Training Administration)
Photonics Engineers (CareerOneStop, U.S. Department of Labor, Employment and Training Administration)

Organization

International Society for Optics and Phontonics (SPIE)
Illuminating Engineering Society
Optica
IEEE Photonics Society

News

Optics News (SPIE)
Optics and Photonics (Nature)
Optics (JSTOR)
Nature of Light (Science Daily)
Optics and Photonics News (Phys.org)
Optics (NPR Archives)

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Expression

Humor

Mirrors (Tim Hunkin, The Rudiments of Wisdom Encyclopedia)
Lenses (Tim Hunkin, The Rudiments of Wisdom Encyclopedia)
Lasers (Tim Hunkin, The Rudiments of Wisdom Encyclopedia)

Toy

Optical Illusions (Grand Illusions)
Optical Toys (Grand Illusions)

Arts

Poem

Each atom absorbs unique light,
Leaving lines that are black as the night.
This absorption occurs
At the bits it prefers,
So the rest of the spectrum stays bright. — DenmarK, absorption spectrum

OEDILF: The Omnificent English Dictionary In Limerick Form

Music

A Capella Science (YouTube Channel)
A Capella Science (Official site)
Tim Blais (Wikipedia)

Recent News from Phys.org …

Light-activated compound kills...
on June 29, 2026 at 4:20 pm
Antibiotic resistance is becoming an accelerating crisis because of the overuse and misuse of antibiotics over many years. The problem is exacerbated when antibiotics wipe out susceptible bacteria but leave resistant bacteria behind to multiply, further spreading resistance. There is an ongoing search for new treatments to fight resistant bacteria, and now researchers may have found a way to successfully treat at least one type of resistant bacteria.
Ultra-faint galaxy discovered near Andromeda may...
on June 29, 2026 at 2:40 pm
A new ultra-faint dwarf galaxy has been discovered in the vicinity of Andromeda (M31), the Milky Way's large neighboring galaxy. The new study, published in Astronomy & Astrophysics suggests that the galaxy, named And XXXVI, is one of the faintest satellite galaxies discovered around Andromeda to date.
UV light patterns thermochromic crystals without...
on June 29, 2026 at 2:20 pm
Color-changing mood rings, forehead fever strips and car-shade indicators all change hues as they warm and cool, thanks to a phenomenon called thermochromism. On a smaller scale, thermochromism is used in nanotechnologies like sensors, electronics and computing. These applications require smart materials that can be patterned into designs without losing structural integrity, which can be difficult.
Age bias discovered in AI
on June 29, 2026 at 2:03 pm
Do responses generated by artificial intelligence systems such as ChatGPT reflect social prejudice? A KAIST research team has quantitatively analyzed and identified age-related stereotypes embedded in the responses of generative artificial intelligence. The study sheds light on the potential impact of hidden AI biases on social perceptions and suggests directions for the development of more inclusive AI.
Why nanoscale droplets don't coalesce and...
on June 29, 2026 at 1:00 pm
Olive oil and water do not naturally mix. Water molecules are polar, having a net electric dipole moment due to the bend angle of about 104.5° between the two oxygen-hydrogen bonds. Olive oil is nonpolar due to its long hydrocarbon chains, which makes it hydrophobic and insoluble in water. Mixtures of the two are called emulsions, and emulsifiers exist that can stabilize them into a thicker temporary or permanent mixture. Cooks use such a technique to make vinaigrette, a salad dressing […]

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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.