Light

Cosma / Communication / Knowledge / Realm / Physical / Force / Electromagnetism / Light
—————————

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)

———————–

Adventures

Explore related posts on Cosma …

Milky Way Lost & Found - Have you seen the Milky Way? You may think that you have, but are you sure? Unless you live in an extremely remote area, or you’ve visited one, then you probably haven’t seen our own galaxy, the Milky Way, very well, or at all. Worse yet, you may not even realize that it’s missing. The … Continue reading Milky Way Lost & Found

———————–

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)

———————-

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)

————————–

Preservation

—————————

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)

———————-

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 …

How to keep electricity costs down amid uncertain...
on October 29, 2026 at 11:40 am
Keeping the lights on nationwide is a feat of engineering that depends on millions of miles of power lines and thousands of power-generation plants.
The phantom lighthouse: New research explains one...
on October 28, 2026 at 11:40 pm
There are two lighthouses on Lady Elliot Island, at the southernmost tip of Australia's Great Barrier Reef. The first was built in 1873, but was decommissioned in 1995 when the second took over the job of warning ships off the reef. Visitors to the island, however, regularly report seeing signs of a third lighthouse. At night the beams of a nonexistent phantom lighthouse are seen far off, shining on the horizon.
Atomic magnetism reveals why iron, but not...
on October 28, 2026 at 11:00 pm
Two nearly identical materials have completely different chemical behavior. Research teams at the University of Vienna and TU Wien studied catalysts that use the energy of sunlight to produce ammonia. Surprisingly, when the three iron atoms that form tiny triangles in these catalysts are replaced by chromium atoms, the chemical reaction no longer takes place.
Q&A: Decoding the cell—a conversation with a...
on October 28, 2026 at 9:40 pm
Computational biologist Christina Leslie, Ph.D., has spent nearly two decades at Memorial Sloan Kettering Cancer Center (MSK) building computational tools that help make sense of some of the most complex data in biology.
Rarely seen deep-sea barreleye fish filmed in 4K
on October 28, 2026 at 9:00 pm
During a recent expedition aboard the research vessel David Packard, MBARI scientists encountered a rarely seen barreleye fish (Macropinna microstoma). This sighting is MBARI's 11th observation of this unique deep-sea fish with a transparent head.

——–
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

——
Notes

1. The resources on this page are are organized by a classification scheme developed exclusively for Cosma.