Browse All 842 Physics Terms A–Z

Wave Function Quantum & Atomic Physics m^(-3/2) (in 3D space) A complex-valued mathematical function containing all the physical information about the state of an isolated quantum mechanical system. ψ(x, t) = A e^(i (k x - ω t))

Wave Number Waves, Oscillations & Acoustics rad/m (or m⁻¹) A spatial frequency measure expressing the number of radians or wave cycles per unit distance. k = 2π / λ

Wave Packet Waves, Oscillations & Acoustics m A short localized burst or envelope of wave energy formed by the superposition of multiple waves with slightly different frequencies. Δx Δk ≥ ½

Wave-Particle Duality Quantum & Atomic Physics Dimensionless Concept The fundamental quantum mechanical principle stating that every subatomic entity exhibits both wave-like and particle-like behavior depending on the experimental measurement. E = h ν, p = h / λ

Waveform Waves, Oscillations & Acoustics N/A The visual shape or graph of a signal or wave as a function of time or spatial position. y = f(x - v t)

Weak Nuclear Force Nuclear & Particle Physics Range ~ 10⁻¹⁸ m The short-range fundamental interaction responsible for flavor-changing particle transformations, neutrino interactions, and radioactive beta decay. Mediated by massive W⁺, W⁻, and Z⁰ gauge bosons

Weber-Fechner Law Biophysics & Medical Physics Psychophysical Scale (e.g. dB, Stellar Magnitude) A psychophysical law stating that human subjective sensory perception is proportional to the logarithm of the physical stimulus intensity. p = k ln(S / S₀) (Perceived Sensation = k ln(Stimulus Intensity))

Weight Foundations of Physics N The downward gravitational force exerted on an object's mass by a surrounding gravitational field. W = m g

Wheatstone Bridge Electromagnetism & Electronics Ω (Ohms) An electrical bridge network consisting of four resistor arms used to measure an unknown electrical resistance with high precision. R_x = R₃ (R₂ / R₁) (when balanced: I_galvanometer = 0)

Whistler Waves Plasma Physics Audio Frequency Pitch Glissando (kHz) A right-hand circularly polarized electromagnetic wave mode propagating along magnetic field lines in a magnetized plasma below electron cyclotron frequency. v_phase = c √(ω ω_ce) / ω_pe (For ω ≪ ω_ce)

White Dwarf Astrophysics, Cosmology & Relativity M_☉ (Mass) or R_Earth (Radius) The dense stellar remnant remaining after a low-to-medium mass star exhausts its core nuclear fuel and sheds its outer layers. P_deg ∝ ρ^(5/3) (Electron Degeneracy Pressure)

Wien's Displacement Law Thermodynamics & Statistical Physics m·K The physical law stating that peak emission wavelength of a blackbody spectrum is inversely proportional to its absolute temperature. λ_max T = b ≈ 2.89777 × 10⁻³ m·K

Work Classical Mechanics J (N·m) The scalar energy transferred to or from an object by a force acting through a displacement. W = F · d = |F| |d| cos θ

Work Hardening Condensed Matter & Materials Physics MPa (Increased Yield Strength) The strengthening of a metal by plastic deformation, caused by dislocation multiplication and entanglement obstructing further slip. σ_y = σ₀ + α G b √ρ_dislocation (Taylor Relation)

Work-Energy Theorem Classical Mechanics J The principle stating that net work done by all forces acting on an object equals the net change in its kinetic energy. W_net = ΔKE = ½ m vf² - ½ m vi²

Wormhole Astrophysics, Cosmology & Relativity Einstein-Rosen Bridge Topology A hypothetical topological feature of spacetime creating a shortcut connecting two separate points in space and time. ds² = -c² dt² + dl² + (r₀² + l²) (dθ² + sin²θ dφ²)

X-Ray Crystallography in Biology Biophysics & Medical Physics Å or nm (Structural Resolution) An experimental biophysical technique determining the 3D atomic structure of biological macromolecules from X-ray diffraction patterns of crystallized proteins or nucleic acids. n λ = 2 d sin θ (Bragg's Law for Macromolecules)

X-ray Imaging Biophysics & Medical Physics keV (Photon Energy) & μ (Attenuation Coefficient in cm⁻¹) A diagnostic medical imaging modality using differential photoelectric attenuation of X-rays passing through human tissue to form 2D projection shadowgraphs. I(x) = I₀ e^(-μ x) (Beer-Lambert Attenuation)

Young's Double Slit Experiment Optics m The classic experiment demonstrating wave-particle duality and wave nature of light via interference fringes produced by coherent light passing through two narrow parallel slits. y_m = m λ D / d (Bright), y_m = (m + ½) λ D / d (Dark)

Young's Modulus Condensed Matter & Materials Physics Pa or GPa (Gigapascals) A mechanical property measuring the tensile or compressive stiffness of a solid material in its linear elastic deformation regime. E = σ / ε = (F / A) / (ΔL / L₀)

Z-Pinch Plasma Physics MA (Mega-amperes Current) A plasma confinement geometry where an axial electric current passed through a plasma column generates a self-pinching azimuthal magnetic field. Bennett Relation: I² = (8 π / μ₀) N k_B (T_e + T_i)

Zeeman Effect Quantum & Atomic Physics eV (Energy Shift) The splitting of atomic spectral lines into multiple closely spaced components in the presence of an external static magnetic field. ΔE = g_L μ_B m_j B

Zener Diode Electromagnetism & Electronics V (Volts) A heavily doped silicon p-n junction diode designed to operate safely in reverse breakdown mode to maintain a precise reference voltage. V_out = V_Z (constant in reverse breakdown)

Zero Error Foundations of Physics Various A systematic error that occurs when a measuring instrument displays a non-zero reading when the actual quantity being measured is zero. True Value = Observed Value - Zero Error

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