Physics

Wave function (quantum state and probability amplitude) Wave function A wave function is the complex-valued mathematical object that encodes a quantum system's probability amplitudes. Its modulus squared gives measurable probabilities and its evoluti…

Wave–particle duality: the quantum nature of light and matter Wave–particle duality Wave–particle duality describes how quantum objects show both wave-like interference and particle-like localization; modern quantum theory explains these behaviors via the wavefunc…

Waveform: shapes, types, and uses in sound and signals Waveform A waveform is the shape of a wave or signal over time. This article explains basic parameters, common waveform types, historical and analytical context, and practical applications…

Wavefunction collapse in quantum mechanics Wavefunction collapse Wavefunction collapse is the postulated change from a quantum superposition to a definite outcome during measurement. This article explains the idea, history, key interpretations,…

Wavelength Distance over which a periodic wave's shape repeats; relates to frequency and speed and is central to optics, acoustics, and wave physics.

Weak interaction (weak nuclear force) Weak interaction One of the four fundamental forces, the weak interaction governs certain types of particle transformations such as beta decay, involves W and Z bosons, and unifies with electromagn…

Weber (unit) — SI unit of magnetic flux Weber (unit) The weber (Wb) is the SI derived unit of magnetic flux, equal to one volt-second. It relates to the tesla (Wb/m²), is named for Wilhelm E. Weber, and is used across electromagnetis…

Weight (physics): force of gravity on an object Weight Weight is the gravitational force acting on an object. Distinct from mass, it is a vector force measured in newtons and varies with location and acceleration; common usage often co…

Wolfgang Pauli Austrian-born theoretical physicist known for the Pauli exclusion principle, Pauli matrices, the neutrino hypothesis, and major contributions to quantum mechanics; Nobel Prize in P…

Work (physics): definition, formulas, examples, and relation to energy Work (physics) Work in physics is the transfer of energy by a force acting through a displacement. This article explains definitions, sign conventions, formulas, examples, units, and connections…

Work (thermodynamics) Energy transfer by organized macroscopic forces in thermodynamic processes, commonly expressed as mechanical, electrical or pressure-volume work; distinct from heat and path-depend…

World line (spacetime trajectory) World line A world line is the path an object traces through spacetime, showing its history and causal relations. It is fundamental to relativity, causal structure, and the distinction betwee…

X-rays: electromagnetic radiation — wavelengths, interactions, imaging and medical uses X-ray Overview of X-rays as electromagnetic radiation: wavelengths and energies, interactions with matter, imaging methods (radiography, CT), medical applications, production and safety…

Yard (unit of length) Yard The yard (abbrev. yd) is a unit of length used in the Imperial and United States customary systems; equal to 3 feet, 36 inches, or exactly 0.9144 metres since 1959.

Young–Laplace equation Relation between pressure jump and curvature of a fluid interface, linking surface tension, capillarity and the physiological Laplace law for hollow organs.

Young's double-slit experiment: wave–particle duality and quantum interference Young's double-slit experiment A clear, concise overview of Young's double-slit experiment: its setup, historical origin, key observations with light and particles, and the experiment's role in revealing wave–pa…

Young's modulus: definition, meaning, measurement and applications Young's modulus Young's modulus quantifies elastic stiffness: the ratio of tensile stress to tensile strain in the linear elastic region of a material. It explains how materials stretch or compres…

Zeroth Law of Thermodynamics: Thermal Equilibrium and the Definition of Temperature Zeroth law of thermodynamics The zeroth law states that thermal equilibrium is transitive: if A is in equilibrium with B and B with C, then A is with C. It underpins the concept of temperature and how thermome…