light: Quick Facts

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Last updated

Oct. 22, 2026

Facts

Also Known As	optical spectrum • visible radiation • visible spectrum

Photos and Videos

A horizontal gradient bar displays the visible light spectrum from violet to red, labeled with corresponding frequency in terahertz, wavelength in nanometers, and photon energy in electron volts.

Marble bust of Pythagoras, the ancient Greek mathematician and philosopher, showing a bearded man with a head covering and calm expression.

English Franciscan philosopher Roger Bacon

Galileo: telescope

Law of reflection diagram showing an incident ray and reflected ray meeting a flat surface at equal angles on either side of a dashed line normal to the surface, theta 1 equals theta 2.

Diagram showing light from a bee reflecting off a vertical plane mirror into an observer's eye; equal angles of incidence and reflection produce a virtual bee image behind the mirror.

Diagram showing several light rays striking a rough surface at different angles, with the reflected rays scattering in multiple directions, illustrating diffuse reflection.

$Snell's law diagram showing an incident ray striking the boundary between media n1 and n2, reflecting at equal angle theta 1 and refracting toward the normal at angle theta 2.$

The discovery of light's wave-particle duality

$Understand how diffraction of light affects stellar images$

Why do stars look pointy to humans?

What would traveling at light speed really look like?

Understand the concept of teleportation and how quantum mechanics makes photon teleportation possible

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Topics

monochromatic light geographic range luminous range transmission factor incoherent light corpuscular theory of light white light polarized light colour blue light time electromagnetism gravity relativity chemical reaction X-ray space-time gamma ray ultraviolet radiation force

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Key People

Isaac Newton

Isaac Newton

English physicist and mathematician

Portrait of Albert Einstein in a suit and tie, looking slightly to the side with a neutral expression.

Albert Einstein

German-American physicist

James Clerk Maxwell

James Clerk Maxwell

Scottish mathematician and physicist

Roger Bacon

Roger Bacon

English philosopher and educational reformer

How did Ptolemy explain retrograde motion?

Ptolemy

Egyptian astronomer, mathematician, and geographer

Fresnel, detail of an engraving by Ambroise Tardieu after a contemporary portrait, 1825

Augustin-Jean Fresnel

French physicist

Edwin H. Land

Edwin Herbert Land

American inventor and physicist

Thomas Young, engraving

Thomas Young

British physician and physicist

illustration of Robert Hooke's law of elasticity of materials

Robert Hooke

British scientist

François Arago

François Arago

French physicist

Johann Lambert, detail of a lithograph by Gottfried Englemann, after a portrait by Pierre-Roch Vigneron

Johann Heinrich Lambert

Swiss-German scientist and philosopher

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Sir David Brewster

Scottish physicist

Pyotr Nikolayevich Lebedev

Pyotr Nikolayevich Lebedev

Russian physicist

Sir Frank Dyson, 1927.

Sir Frank Dyson

British astronomer

Gullstrand

Allvar Gullstrand

Swedish ophthalmologist

Malus, engraving by A. Tardieu after a painting

Étienne-Louis Malus

French physicist

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Hendrik Anthony Kramers

Dutch physicist

Italian-born physicist Dr. Enrico Fermi draws a diagram at a blackboard with mathematical equations. circa 1950.

Physics and Natural Law

27 True-or-False Questions from Britannica’s Most Difficult Science Quizzes

Italian physicist Guglielmo Marconi at work in the wireless room of his yacht Electra, c. 1920.

All About Physics Quiz