Physics

Motion (disambiguation) Different meanings of motion: physical movement, legal or parliamentary proposals, motion pictures and detection, robotics planning, perception, and software.

Move — meanings across motion, law, computing, organizations and culture Move “Move” is a common English word with senses in physical motion, migration, legal procedure, computing commands, brand names, and music. This article surveys primary meanings, histo…

Movement (Motion): Concepts, Frames of Reference, and Physical Principles Movement An overview of movement (motion): definitions, reference frames, kinematics vs dynamics, historical development, examples, and why motion matters in science and everyday life.

Muon (elementary particle) Muon A muon is a charged, spin‑1/2 lepton similar to the electron but heavier and unstable. It plays roles in particle physics, cosmic rays, muonic atoms and applications such as imagin…

Muzzle velocity Muzzle velocity is the speed of a projectile as it leaves a firearm's barrel. It affects trajectory, energy, and effective range and is influenced by firearm design, ammunition, an…

Navier–Stokes equations: theory, applications, and mathematical challenges Navier–Stokes equations Overview of the Navier–Stokes equations, their physical meaning, common forms, applications in science and engineering, and the central mathematical questions about existence and s…

Neutral particle A neutral particle is a particle with zero electric charge. This article explains what neutrality means, how neutral particles interact, historical milestones, common examples, and…

Neutrino: properties, origins, detection, and scientific importance Neutrino Neutrinos are neutral, nearly massless elementary particles produced in nuclear processes. This article describes their properties, types, production, detection methods, history, a…

Neutron (subatomic particle) Neutron A neutral baryon found in atomic nuclei, made of quarks. Discovered in 1932, neutrons determine isotopes, enable nuclear reactions and scattering probes, and play key roles in astr…

Neutron moderator: role, types, and importance in nuclear reactors Neutron moderator A neutron moderator is a material used to slow fast neutrons so they can sustain controlled fission in thermal reactors. This article explains how moderators work, common types, us…

Newton (unit of force) Newton (unit) SI derived unit of force defined as the force required to accelerate 1 kilogram at 1 metre per second squared; named for Isaac Newton and used worldwide in science and engineering.

Newton metre (N·m) — SI unit of torque and moment Newton metre The newton metre (N·m) is the SI derived unit for torque and moment of force. Dimensionally equal to a joule but conceptually distinct; used in mechanics, engines, and engineering…

Newton's Law of Cooling: principle, equation, applications and limits Newton's Law of Cooling Newton's Law of Cooling describes how an object's temperature approaches its environment over time. It is modeled by a first‑order linear differential equation with broad applicati…

Newton's law of universal gravitation Statement and explanation of Newton's universal law of gravitation, its formula, history, applications, units, limitations, and key properties in classical physics.

Newton's laws of motion Three foundational principles by Isaac Newton that describe how forces affect motion in classical mechanics and underpin much of engineering and physics.

Newtonian fluid A Newtonian fluid exhibits a linear relationship between shear stress and shear rate with a constant viscosity; covers definition, mathematics, examples, history, and distinction f…

Nodal Plane (Quantum Wavefunction Zero Region) Nodal plane A nodal plane is a region where a quantum wavefunction is zero. It appears in atomic and molecular orbitals, shapes orbital symmetry, affects bonding and spectroscopy, and helps cl…

Non-Newtonian fluids: properties, examples, and everyday uses Non-Newtonian fluid Fluids whose flow behavior changes with applied stress or time. Covers defining features, common examples (oobleck, blood, ketchup), simple experiments, and practical applications.

Normal force: definition, behavior on surfaces, and common examples Normal force Overview of the normal force: the contact force perpendicular to a surface, its magnitudes on flat and inclined planes, role in friction and scales, and practical examples.

Normal lens (standard lens) in photography Normal lens A normal (standard) lens has a focal length close to the image sensor's diagonal, producing a natural perspective with minimal distortion. Common on many formats, it is versatile f…

Nuclear: concepts, technologies, and global significance Nuclear Comprehensive overview of 'nuclear' — from atomic nuclei and reactions to reactors, weapons, waste, and related scientific and mathematical meanings.

Nuclear chain reaction: principles, types, history and applications Nuclear chain-reaction Overview of nuclear chain reactions: how fission produces self-sustaining sequences, criticality and control, differences between reactors and weapons, history, safety, and common…

Nuclear energy Energy released by nuclear reactions—mainly fission and (in research) fusion—used for electricity, propulsion, medical isotopes and industrial processes. Covers principles, history…

Nuclear explosion: causes, effects, and historical context Nuclear explosion An overview of nuclear explosions: how they occur, their characteristic effects, historical uses, and distinctions from non-nuclear accidents and conventional explosions.

Nuclear fallout: causes, characteristics, history, and protection Nuclear fallout Nuclear fallout is radioactive material deposited after a nuclear detonation or reactor release. This article covers formation, types, health effects, notable incidents, measuremen…

Nuclear fission: process, history, applications, and key concepts Nuclear fission Nuclear fission is the splitting of heavy atomic nuclei that releases energy and neutrons. This article explains how fission works, its history, uses in reactors and weapons, and i…

Nuclear force: the interaction that binds atomic nuclei Nuclear force The nuclear force is the short-range interaction that holds protons and neutrons together inside atomic nuclei. It is a residual effect of the strong interaction and underpins nucl…

Nuclear fuel: types, properties, and role in energy production Nuclear fuel Materials used to produce energy by nuclear processes, their types, characteristics, fuel cycles, uses in reactors and radioisotope devices, and key safety and waste considerations…

Nuclear fusion: process, role in stars, and prospects for power Nuclear fusion Nuclear fusion is the joining of light atomic nuclei into heavier ones, releasing energy. This article explains the physics, stellar role, confinement methods, earthly experiments,…

Nuclear magnetic resonance (NMR) Nuclear magnetic resonance NMR is a physical phenomenon and analytical technique in which nuclei with nonzero spin absorb and re-emit radiofrequency energy in a magnetic field; it underpins spectroscopy, str…

Nuclear physics: structure, reactions, history and applications Nuclear physics Study of atomic nuclei, their constituents and interactions; covers models, decay and reactions, applications in energy and medicine, historical milestones and how it differs from…

Nuclear power: principles, reactor types, waste, safety and future prospects Nuclear power Comprehensive overview of nuclear power: how reactors produce electricity, main reactor types and fuel cycle, waste and safety issues, historical incidents, and ongoing development…

Nucleon (proton and neutron) Nucleon A nucleon is any particle—proton or neutron—found in an atom's nucleus; composite baryons made of quarks that determine nuclear properties, binding, isotopes, and many applications…

Nucleosynthesis: formation and origins of the chemical elements Nucleosynthesis Nucleosynthesis is the set of astrophysical processes that create atomic nuclei from lighter particles. Covers Big Bang, stellar, explosive, and neutron-capture pathways and their…

Ohm (unit of electrical resistance) Ohm The ohm (Ω) is the SI derived unit of electrical resistance, defined by R = V/I, named for Georg Ohm; it links voltage, current and material properties and appears in circuits, mea…

Ohm's law: relationship between voltage, current and resistance Ohm's law Ohm's law describes the linear relationship between voltage, current and resistance in many electrical conductors, its limits, historical origin, common uses, and examples of non‑o…

Optical depth (attenuation of radiation) Optical depth Optical depth is a dimensionless measure of how much light or other radiation is absorbed or scattered along a path; it controls transmission, distinguishes optically thin/thick me…

Optical filter: types, performance and common applications Optical filter A concise guide to optical filters: how they shape light by wavelength, principal types (absorptive, interference, neutral density), key performance metrics, development, and main…

Optical gain medium Material or system in which light is amplified by stimulated emission. Describes operation, types (solid, gas, liquid, semiconductor, fiber), pumping methods, history, and common a…

Optics: The Science and Technology of Light Optics Overview of optics: basic principles, key phenomena, historical development, common devices and modern applications including fibers and imaging technologies.

P-type semiconductor A p-type semiconductor is created by adding trivalent impurities that produce hole majority carriers; used widely in diodes, transistors and photovoltaic devices and contrasted wit…

Pair production: creation of electron–positron pairs from high-energy photons Pair production Pair production is the conversion of a high-energy photon into an electron and a positron in the electromagnetic field of a nucleus or charged particle; important in high-energy ph…

Parity (P symmetry) in Physics Parity Parity is the symmetry under spatial inversion (mirror reflection). It classifies how physical systems behave when coordinates are flipped and is central to quantum mechanics, part…

Particle: types, structure, properties, history and applications Particle An accessible overview of particles — from macroscopic grains to elementary quarks — covering scales, key properties, historical development, and practical uses in science and tech…

Particle accelerator Machines that accelerate charged particles to high speeds for research and practical applications; include linear and circular designs like cyclotrons and large colliders.

Particle detector: principles, types, history and applications Particle detector Overview of particle detectors — devices that detect and characterize particles from decay, cosmic rays or accelerators; principles, common detector types, history, and practical u…

Particle physics: fundamentals, history, and applications Particle physics Particle physics studies the elementary constituents of matter and their interactions, using quantum field theory, symmetry principles, and large-scale experiments to probe the sma…

Particle size: definitions, measurement and practical importance Particle size (general) An overview of particle size concepts, how sizes are defined and measured, and why size matters in materials, aerosols, pharmaceuticals and soils.