Physics terms starting with F

Faraday's Law of Induction Electromagnetism & Electronics V (Volts) Maxwell's third equation stating that a time-varying magnetic flux through a closed conductive loop induces an electromotive force (EMF) around the loop. E = -dΦ_B / dt, ∇ × E = -∂B/∂t

Fast Fourier Transform (FFT) Mathematical & Computational Physics Computational FFT Algorithm An efficient algorithm that computes the Discrete Fourier Transform (DFT) of a sequence in O(N log N) operations instead of O(N²). Cooley-Tukey Divide-and-Conquer: O(N log N) vs O(N²)

Fatigue Condensed Matter & Materials Physics Cycles to Failure N_f The progressive structural weakening and microcrack failure of a material subjected to repeated cyclic loading stresses below its ultimate tensile strength. Basquin's Relation: S_a = σ'_f (2 N_f)^b

Fermat's Principle Optics s (or m) The fundamental principle stating that light traveling between two points follows the path that requires the stationary (usually minimum) optical path time. Optical Path Length L = ∫ n(s) ds = extremum

Fermi Energy Quantum & Atomic Physics eV or Joules The highest occupied kinetic energy state of non-interacting fermions in a quantum system at absolute zero temperature (0 K). E_F = (ℏ² / (2 m)) (3 π² n)^(2/3)

Fermi Level Condensed Matter & Materials Physics eV (Chemical Potential) The thermodynamic Fermi-Dirac chemical potential representing the energy level at which the probability of electron occupancy is exactly 50% at finite temperature. f(E) = 1 / (e^((E - E_F) / (k_B T)) + 1)

Fermi Paradox Astrophysics, Cosmology & Relativity Astronomical Paradox The apparent contradiction between high probabilistic estimates for the existence of extraterrestrial civilizations and the complete lack of physical evidence or contact. Enrico Fermi: 'Where is everybody?'

Fermions Quantum & Atomic Physics Dimensionless Particle Class Subatomic particles possessing half-integer intrinsic spin that obey Fermi-Dirac statistics and the Pauli Exclusion Principle. Spin = ½, ³/₂, ⁵/₂...

Ferromagnetism Electromagnetism & Electronics Dimensionless A strong magnetic phenomenon in which atomic magnetic moments spontaneously align parallel into localized magnetic domains, producing permanent magnetization. μ_r ≫ 1 (μ_r ~ 1,000–100,000)

Feynman Diagram Nuclear & Particle Physics Calculational Diagram Visual pictorial representations of mathematical expressions describing the quantum interaction and scattering behavior of subatomic particles. Pictorial matrix elements M_fi in QFT perturbational expansions

Fick's Laws of Diffusion Biophysics & Medical Physics mol/(m²·s) (Flux J) & m²/s (Diffusion Coefficient D) Physical laws describing solute diffusion mass transport across biological concentration gradients. 1st: J = -D (dC / dx); 2nd: ∂C / ∂t = D (∂²C / ∂x²)

Field-Reversed Configuration (FRC) Plasma Physics Dimensionless High Beta ⟨β⟩ ~ 0.9 A high-beta compact toroid magnetic confinement concept where a closed-poloidal-field plasma torus is sustained inside a simple linear solenoid magnet. Average Beta ⟨β⟩ ≈ 1 (High-Beta Compact Toroid)

Fine Structure Quantum & Atomic Physics eV (Energy Splitting) The small splitting of atomic spectral lines resulting from relativistic mass corrections and spin-orbit coupling. E_fine ~ α² E_n, α ≈ 1 / 137

Finite Difference Method Mathematical & Computational Physics Grid Discretization Method A numerical method for solving differential equations by approximating derivatives with finite difference quotients on a discretized grid. f'(x) ≈ (f(x + h) - f(x - h)) / (2 h), f''(x) ≈ (f(x+h) - 2f(x) + f(x-h)) / h²

Finite Element Method (FEM) Mathematical & Computational Physics Numerical Mesh Method A numerical technique for solving complex partial differential equations by subdividing a large physical domain into smaller, simpler finite sub-domains called elements. K u = f (Global Stiffness Matrix Equation)

Finite Potential Well Quantum & Atomic Physics eV or Joules A quantum potential well model with barriers of finite energy height V₀. V(x) = V₀ for |x| > a, V(x) = 0 for |x| ≤ a

First Law of Thermodynamics Thermodynamics & Statistical Physics J A statement of universal energy conservation applied to thermodynamic systems, asserting that internal energy change equals net heat added minus work done by the system. ΔU = Q - W

Fluorescence Quantum & Atomic Physics Nanoseconds (Lifetime) The rapid absorption of light at a shorter wavelength followed by immediate emission of light at a longer wavelength. h ν_emitted < h ν_absorbed (Stokes Shift)

Fluorescence Microscopy Biophysics & Medical Physics nm (Spatial Resolution) An optical microscopy technique utilizing fluorophores excited by specific light wavelengths to image cellular structures with high contrast. Abbe Diffraction Limit: d_min = λ / (2 NA) ≈ 200 nm

Fluoroscopy Biophysics & Medical Physics Frames per Second (fps) & Dose Rate (mGy/min) A dynamic X-ray imaging technique obtaining real-time moving video images of interior anatomical structures and contrast agents. Real-time continuous low-dose X-ray video acquisition

Fokker-Planck Equation for Plasmas Plasma Physics Kinetic Collision Operator The kinetic equation describing the time evolution of a plasma velocity distribution function subject to small-angle Coulomb collisions. (∂f / ∂t)_coll = -∇_v · (A f) + ½ ∇_v ∇_v : (B f)

Force Classical Mechanics N (kg·m/s²) A vector interaction that, when unopposed, alters the state of motion or deforms a physical body. F = m a = dp/dt

Forced Oscillations Waves, Oscillations & Acoustics m Oscillations produced in a system subjected to a periodic external driving force. m (d²x/dt²) + b (dx/dt) + k x = F0 cos(ω t)

Fourier Series Mathematical & Computational Physics Harmonic Series Expansion An expansion of a periodic function f(x) into an infinite sum of orthogonal sine and cosine harmonic functions. f(x) = a₀/2 + ∑_(n=1)^(∞) [a_n cos(n x) + b_n sin(n x)]

Terms starting with F