Corpuscular theory of light

The historical theory that light consists of tiny particles, or corpuscles, emitted by luminous objects and traveling along straight paths. Isaac Newton’s version explained reflection and refraction through particle motion.

Reflection: The change in direction of a wave or ray at a boundary, returning it to its original medium. Corpuscles were thought to rebound from surfaces, explaining why the angle of reflection equals the angle of incidence.
Isaac Newton: English mathematician and natural philosopher who formulated classical mechanics and a major theory of light. His influential version treated light as corpuscles and appeared in his 1704 book Opticks.
Wave theory of light: The account that light propagates as waves rather than as streams of material particles. It explained diffraction and interference more naturally than Newton’s corpuscular theory.
Newton's theory of color: Newton’s account that white light contains rays of different refrangibility associated with distinct colors. His prism experiments linked the corpuscular view to a lasting account of color composition.
Refraction: The change in direction of light as it crosses between materials in which it travels at different speeds. Newton’s model attributed bending to forces exerted by a boundary on passing corpuscles.
Opticks: Isaac Newton’s 1704 book on the nature and behavior of light, color, and optical instruments. Newton presented his corpuscular views alongside experiments on reflection, refraction, and color.
Diffraction: The spreading and bending of waves as they pass openings or edges. Light’s diffraction patterns resisted explanation by corpuscles traveling only in straight lines.
Fizeau experiment: Hippolyte Fizeau’s 1851 experiment measuring how moving water affects the speed of light passing through it. Its result supported the wave theory’s prediction where corpuscular accounts had expected a different effect.
Newton's rings: Concentric light and dark rings formed when a curved surface lies close to a flat one. Their periodic pattern challenged a purely corpuscular account and prompted Newton to propose fits and starts in light.
Pierre Gassendi: French philosopher and scientist who revived ancient atomism and defended a particle-based account of matter. His revival of atomist ideas formed part of the intellectual background for corpuscular explanations.

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