Browse All 842 Physics Terms A–Z

Thermohaline Circulation Geophysics & Environmental Physics Sv (Sverdrups = 10⁶ m³/s) The global deep-ocean density-driven circulation loop powered by surface variations in seawater temperature (thermo) and salinity (haline). Density ρ = ρ(T, S, P) (Function of Temperature and Salinity)

Thin Film Interference Optics m The interference phenomenon occurring when light waves reflected from the top and bottom boundaries of a thin transparent film superimpose. 2 n t cos θ = m λ (Constructive with phase shift)

Third Law of Thermodynamics Thermodynamics & Statistical Physics J/K The law stating that as system temperature approaches absolute zero (0 K), entropy of a pure crystalline substance approaches a minimum constant value of zero. lim (T → 0) S = 0

Threshold of Hearing Waves, Oscillations & Acoustics W/m² (0 dB) The minimum sound pressure level or intensity audible to a healthy human ear at 1000 Hz. I0 = 10⁻¹² W/m² (0 dB SPL, P0 = 20 µPa)

Threshold of Pain Waves, Oscillations & Acoustics W/m² (120-130 dB) The upper sound intensity limit above which acoustic vibrations cause physical discomfort and immediate structural damage to human ears. I_pain ≈ 1 W/m² (120 - 130 dB SPL)

Tidal Friction Geophysics & Environmental Physics ms/century (Length of Day Increase) The gravitational interaction where ocean tidal bulges drag ahead of the Earth-Moon axis, causing frictional dissipation of Earth's rotational energy. dΩ/dt < 0 (Earth rotation slowing by ~2.3 ms/century)

Timbre Waves, Oscillations & Acoustics N/A The subjective tone quality or color of a musical sound that distinguishes different instruments playing the same fundamental pitch and loudness. Fourier Spectrum Balance

Time Foundations of Physics s A fundamental physical quantity used to sequence events, quantify durations, and measure rates of change in the universe. Δt = t2 - t1

Time of Flight Classical Mechanics s The total duration a projectile spends in the air from launch until returning to its landing elevation. T = (2 v0 sin θ) / g

Tissue Viscoelasticity Biophysics & Medical Physics Pa (Modulus) & Pa·s (Viscosity η) The mechanical property of biological tissues exhibiting both elastic solid-like storage and viscous fluid-like energy dissipation under deformation. Maxwell / Kelvin-Voigt Models: σ(t) = E ε(t) + η (dε / dt)

Tokamak Plasma Physics Dimensionless Safety Factor q A toroidal magnetic confinement fusion device that utilizes external magnetic coils and an internal driven plasma current to create a helical magnetic field. q = (r B_toroidal) / (R B_poloidal)

Topological Insulator Condensed Matter & Materials Physics Quantum Phase Class A quantum material that behaves as an electrical insulator in its 3D interior bulk but features robust conducting metallic states on its 2D surface boundary. Z₂ Topological Invariant ν = 1

Toroid Electromagnetism & Electronics T (Tesla) A doughnut-shaped ring wrapped with insulated wire that confines a uniform magnetic field completely within its circular core. B = (μ₀ N I) / (2π r)

Torque Classical Mechanics N·m The rotational equivalent of linear force, measuring the effectiveness of a force in causing angular acceleration about an axis. τ = r × F = r F sin θ

Total Internal Reflection Optics Degrees (°) The complete reflection of a light ray inside an optically denser medium when striking the boundary with a rarer medium at an angle exceeding the critical angle. sin θ_c = n2 / n1 (where n1 > n2)

Transformer Electromagnetism & Electronics Dimensionless (Turns Ratio) A static AC electrical device that transfers electrical energy between circuits through mutual electromagnetic induction to step up or step down AC voltage. V_s / V_p = N_s / N_p = I_p / I_s

Transverse Wave Waves, Oscillations & Acoustics m A wave in which medium particles oscillate perpendicular to the direction of wave energy propagation. y(x,t) = A sin(k x - ω t)

Troposphere Geophysics & Environmental Physics km (Altitude ~0 to 12 km) The lowest layer of Earth's atmosphere, extending from the surface up to the tropopause (~7 to 18 km), containing ~80% of atmospheric mass and virtually all water vapor. dT / dz ≈ -6.5 °C/km (Environmental Lapse Rate)

Tsunami Waves, Oscillations & Acoustics m/s A series of extremely long-wavelength ocean water waves generated by sudden vertical displacement of the seafloor. v = √(g d)

Twin Paradox Astrophysics, Cosmology & Relativity Years (Elapsed Proper Time) A famous thought experiment in special relativity where one twin travels into space at high speed and returns younger than the twin who stayed on Earth. τ_traveler = τ_stay / γ (Asymmetric acceleration worldlines)

Two-Stream Instability Plasma Physics s⁻¹ (Growth Rate Im(ω)) A fundamental electrodynamic plasma instability that occurs when two counter-streaming particle beams or an electron beam injected into a stationary plasma excite growing electrostatic waves. 1 = (ω_pe1² / (ω - k v₁)²) + (ω_pe2² / (ω - k v₂)²)

Tyndall Effect Optics N/A The scattering of a light beam by colloidal particles or tiny suspended matter in a fine suspension or transparent medium. N/A

Type I & II Superconductors Condensed Matter & Materials Physics T or A/m (Critical Magnetic Field) The classification of superconductors based on their magnetic field response and flux penetration characteristics. Type I: Single H_c; Type II: Lower H_c1 and Upper H_c2

Unit Cell Condensed Matter & Materials Physics Å³ or nm³ (Unit Cell Volume) The smallest repeating structural unit of a crystal lattice that generates the entire 3D crystal structure through simple translational repetition. V_cell = a · (b × c)

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