Physics

Combined gas law Relationship among pressure, volume and temperature of a fixed amount of gas; combines Boyle's, Charles's and Gay-Lussac's laws and leads toward the ideal gas law.

Composite particle An overview of composite particles: definition, constituents (quarks, nucleons), classification (hadrons, baryons, mesons), size and structure, experimental probes, and modern deve…

Compressive strength: definition, measurement, and practical importance Compressive strength Compressive strength is the maximum uniaxial compressive stress a material can withstand before failure. It is a key property for concrete, ceramics, rock, metals and structural de…

Compressive Stress: Definition, Behavior, Measurement, and Engineering Uses Compressive stress Compressive stress describes internal force per area that shortens or compacts materials. Covers definition, formulas, failure modes (brittle/ductile), testing, design consideratio…

Compton scattering Compton scattering is the inelastic scattering of high-energy photons by electrons, producing a measurable increase in photon wavelength and providing key evidence for the particle…

Condensed matter physics Branch of physics that studies properties and behavior of densely packed phases of matter — solids and liquids — including emergent collective phenomena and their technological app…

Conduction: heat and electrical energy transfer Conduction Conduction is the transfer of energy through direct contact—commonly heat or electric current—governed by material properties and important in engineering, electronics, and everyda…

Conservation law (physics) Conservation law Principles stating that certain physical quantities remain constant in time or are locally conserved; covers mass, energy, momentum, charge, formal statements, origins, and applica…

Conservation of Energy: Principle, Basis, and Applications Conservation of energy Fundamental physical principle that total energy in an isolated system remains constant; covers forms, mathematical basis (Noether), thermodynamics, everyday examples and limits in…

Convection: heat transfer by fluid motion Convection Convection is heat transfer carried by the bulk motion of fluids. This article describes mechanisms, natural and forced convection, examples, key nondimensional parameters, modelin…

Copenhagen interpretation of quantum mechanics Copenhagen interpretation A major early interpretation of quantum mechanics emphasizing probabilistic outcomes, wavefunction collapse, and complementarity, chiefly developed by Niels Bohr and Werner Heisenb…

Coriolis effect — apparent deflection in rotating frames Coriolis effect The Coriolis effect is the apparent deflection of moving objects observed in a rotating reference frame, responsible for large-scale wind and ocean patterns and important in meteor…

Corium (nuclear reactor) — molten fuel and reactor debris Corium (nuclear reactor) Corium is the molten mixture formed during a severe nuclear reactor core meltdown, containing fuel, structural materials and contaminants; it presents extreme heat, radiation and c…

Cosmic ray High-energy particles from space—mostly protons and atomic nuclei—that strike the atmosphere, produce particle cascades, and provide probes of astrophysical accelerators and space…

Cosmological principle The cosmological principle states that on sufficiently large scales the universe is homogeneous and isotropic. It underpins standard cosmology, guides models like the FLRW metric,…

Coulomb — SI unit of electric charge Coulomb The coulomb (C) is the SI unit of electric charge. Defined as the charge carried by a current of one ampere in one second, it links microscopic electron charge to macroscopic elect…

Coulomb's law: the inverse-square law of electrostatic force Coulomb's law Coulomb's law describes the magnitude and direction of the electrostatic force between stationary point charges; it is an inverse-square law central to classical electrostatics and…

CP Violation in Particle Physics: Causes, Experiments, and Cosmological Significance CP violation Explains CP violation: origins in the Standard Model, landmark kaon and B-meson experiments, implications for the matter–antimatter imbalance, and ongoing searches for new sources.

Crest (physics): the peak point of a wave Crest (physics) In physics, a crest is the highest point of a wave cycle. This article explains crests and troughs, amplitude and phase, interference (constructive and destructive), examples, meas…

Critical point (thermodynamics) The critical point is the end of the liquid–gas coexistence curve where liquid and gas become indistinguishable. It marks the onset of the supercritical state and shows characteris…

Cutoff Frequency: threshold in photoemission, filters, and waveguides Cutoff frequency Critical frequency below which a physical response ceases or is strongly attenuated: in photoemission it is the threshold frequency, in filters it marks the roll-off, and in wavegu…

Cyclotron: principles, history, design, and applications Cyclotron An overview of the cyclotron: its invention, operating principles, main components, variants, applications in medicine and industry, and practical considerations for operation and…

Dalton's law of partial pressures Dalton's law Dalton's law states that in a mixture of non‑reacting gases the total pressure equals the sum of the pressures each gas would exert alone. It applies to ideal or low‑pressure gases…

Damping in physical systems: mechanisms, models, and applications Damping Damping is any process that reduces the amplitude of oscillations or vibrations by dissipating energy. This article explains common models, types, mathematical measures, and practi…

Dark matter: the invisible mass that shapes the cosmos Dark matter Dark matter is a non-luminous component of the universe inferred from gravitational effects. It dominates galactic dynamics and cosmic structure formation and is detected only thro…

Degree of Freedom (in physics and engineering) Degree of freedom Number of independent parameters that specify the state or motion of a system. Covers definitions, types (translational, rotational, vibrational), examples, history, and practical…

Density: definition, measurement, examples, and applications Density Density measures how much mass is contained in a given volume. This article explains the formula, units, measurement methods, typical values, historical context, applications, and…

Diamagnetism: Weak magnetic repulsion and its physical basis Diamagnetism Diamagnetism is a universal, typically weak form of magnetism in which materials develop an induced magnetic moment that opposes an applied magnetic field.

Diffraction — wave behavior, patterns, and applications Diffraction Diffraction is the bending and spreading of waves when they encounter edges or openings. It appears for sound, water, light and matter waves and underpins imaging limits, spectrosc…

Dipole: electric and magnetic dipoles, dipole moment and applications Dipole Overview of dipoles in physics: definitions of electric and magnetic dipoles, dipole moment, field behavior, typical examples (molecules, current loops, magnets), applications and…

Dirac equation: relativistic wave equation for spin-1/2 particles Dirac equation A relativistic quantum wave equation introduced by Paul Dirac in 1928 that describes spin-1/2 fermions, predicts antimatter, and underpins modern quantum field theory, condensed-ma…

Direct current (DC): definition, characteristics, history and applications Direct current Direct current (DC) is electric current flowing in a single direction. This article explains its properties, sources, historical development, common uses and how it differs from al…

Dispersion (wave phenomena) Dispersion Dispersion describes how a wave's speed depends on frequency, causing different spectral components to travel at different velocities; it affects optics, water waves, seismic waves…

Dissipation (physics): energy loss, damping, and irreversible processes Dissipation Dissipation in physics describes irreversible loss of organized energy (waves, motion, fields) into heat or microscopic disorder; important in mechanics, thermodynamics, engineerin…

Distance: concepts, calculations, and practical uses Distance An overview of distance as a physical and mathematical concept: how it is measured, computed in geometry, various metrics, historical notes, and practical applications and distinct…

Doppler effect Change in frequency and wavelength of waves observed when there is relative motion between source and observer; important in acoustics, optics, radar, astronomy, and medical imagin…

Doppler radar: measuring motion by frequency shift Doppler radar Doppler radar uses the Doppler effect to determine the radial velocity of targets. It is widely used in weather observation, traffic enforcement, air traffic control and military t…

Down quark: properties, role in matter and significance in particle physics Down quark Summary of the down quark: its basic properties, how it builds protons and neutrons, interactions, role in decays and hadrons, and how it differs from other quark flavors.

Drag (physics): resistance force experienced by objects moving through fluids Drag (physics) Drag is the resistive force a fluid exerts on an object moving through it. This article explains causes, common models, examples, and practical steps to reduce drag in engineering…

Dynamic pressure Dynamic pressure is the kinetic-energy-per-volume of a moving fluid, q = 1/2 ρ v². It appears in Bernoulli’s equation, is measured by pitot tubes, and is central to aerodynamic loa…

Dynamics (mechanics): study of forces and motion Dynamics Dynamics is the branch of mechanics that explains how forces produce changes in motion, covering principles, mathematical formulations, history, and applications across engineering…

Effective range (firearm ballistics) Effective range The distance over which a projectile can be expected to strike a target with acceptable accuracy and effect; shaped by ballistics, weapon and ammunition design, sights, shooter ski…

Einstein field equations Fundamental equations of general relativity relating spacetime curvature to matter and energy, central to modern cosmology, black hole physics, gravitational waves, and numerical r…

Elastic collision An elastic collision is a physical interaction where colliding bodies exchange momentum without net loss of kinetic energy. Covers definitions, conservation laws, formulas, example…

Elastic limit: material behavior before permanent deformation Elastic limit The elastic limit is the maximum stress a material can endure and still return to its original shape; beyond it, permanent (plastic) deformation occurs. Important in design, testin…

Elastic modulus: definition, types, measurement and engineering significance Elastic modulus Elastic modulus quantifies a material's tendency to deform elastically under load. Covers definitions, main types (Young's, shear, bulk), relations, measurement methods, applicatio…

Elasticity Elasticity is the property of returning to an original form after deformation; the term applies in physics, materials science, economics, biology and mathematics with distinct defi…

Elasticity (physics) Elasticity is the property of materials to return to their original shape after deformation. It is quantified by stress, strain, and elastic moduli and underpins springs, structure…