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Condensed Matter & Materials Physics

Seebeck Effect

The direct conversion of a temperature gradient into an electrical voltage across a conductor or semiconductor.

V = S ΔT = S (T_hot - T_cold) μV/K (Seebeck Coefficient S)
Geophysics & Environmental Physics

Seismic Waves (P & S Waves)

Elastic body waves that propagate through Earth's interior during an earthquake, classified as Primary (P) waves and Secondary (S) waves.

v_P = √((K + ⁴/₃ μ) / ρ), v_S = √(μ / ρ) km/s (Seismic Wave Velocities)
Geophysics & Environmental Physics

Seismology

The scientific study of earthquakes and the propagation of mechanical elastic waves through the Earth's interior and surface layers.

v_p = √((K + ⁴/₃ μ) / ρ), v_s = √(μ / ρ) m/s (Wave Speeds)
Quantum & Atomic Physics

Selection Rules

A set of quantum mechanical rules constraining allowed radiative transitions between atomic energy states.

Δl = ±1, Δm_l = 0, ±1 Dimensionless Quantum Rules
Electromagnetism & Electronics

Self-Inductance

The property of an electrical conductor or coil whereby a change in current induces an opposing electromotive force in the conductor itself.

E = -L (dI/dt), L = N Φ_B / I H (Henries = V·s/A)
Condensed Matter & Materials Physics

Semiconductor

A class of crystalline solids possessing electrical conductivity between that of conductors and insulators, controllable by temperature…

σ = e (n μ_e + p μ_h), n_i = √(N_c N_v) e^(-E_g / (2 k_B T)) S/m (Electrical Conductivity)
Electromagnetism & Electronics

Semiconductor Diode

A two-terminal semiconductor device formed by a p-n junction that allows electric current to flow easily in one direction while blocking it…

I = I_s [exp(e V / (k_B T)) - 1] A (Current), V (Voltage)
Electromagnetism & Electronics

Series Circuit

An electrical circuit topology in which components are connected end-to-end sequentially along a single continuous current path.

R_total = R₁ + R₂ + R₃, I_total = I₁ = I₂ = I₃ Ω (Ohms)
Condensed Matter & Materials Physics

Shape Memory Alloys

A class of smart metallic alloys that can be deformed when cold, but return to their original pre-deformed shape when heated above a…

Reversible Austenite (High T) ↔ Martensite (Low T) Phase Shift % (Recoverable Superelastic Strain)
Waves, Oscillations & Acoustics

Shock Wave

A extremely thin propagating pressure disturbance characterized by a nearly instantaneous jump in pressure, temperature, and density.

P2 / P1 = 1 + (2γ / (γ + 1)) (M1² - 1) Pa
Foundations of Physics

SI Units

The International System of Units (SI), the modern metric system used globally as the standard language of science and measurement.

Dimensionless
Foundations of Physics

Significant Figures

The digits in a measured or calculated quantity that carry meaningful contribution to its measurement precision.

Dimensionless
Classical Mechanics

Simple Harmonic Motion

Repetitive periodic motion where restoring force is directly proportional to displacement and acts toward the equilibrium position.

x(t) = A cos(ω t + φ), ω = √(k/m) m, rad/s
Classical Mechanics

Simple Machine

A basic mechanical device that changes the direction or magnitude of an applied force.

MA = F_out / F_in Dimensionless
Optics

Simple Microscope

An optical magnifying instrument consisting of a single converging biconvex lens used to produce an enlarged, upright, virtual image.

M = 1 + (D / f) (Image at near point D) Dimensionless (×)
Astrophysics, Cosmology & Relativity

Singularity

A region in spacetime where gravitational curvature and density become infinite, causing classical general relativity equations to break…

Lim (r → 0): R_μνρσ R^μνρσ → ∞ Infinite Curvature / Density
Plasma Physics

Solar Wind

A continuous supersonic stream of fully ionized magnetoplasma (protons, electrons, alpha particles) expanding outward from the Sun's corona…

v_sw ≈ 300–800 km/s, n_e ≈ 5 cm⁻³ at 1 AU km/s (Velocity) & cm⁻³ (Density)
Geophysics & Environmental Physics

Solar Wind Interaction

The plasma physics interaction between the Sun's supersonic coronal plasma stream and Earth's geomagnetic field.

Bow Shock Formation (Supersonic Magnetosheath Plasma Flow) Plasma Density & Velocity
Electromagnetism & Electronics

Solenoid

A long helical coil of insulated wire that produces a uniform interior magnetic field when an electric current flows through it.

B = μ₀ n I (where n = N / L) T (Tesla)
Waves, Oscillations & Acoustics

Sonar

Sound Navigation and Ranging—a technique utilizing acoustic wave propagation underwater to navigate, communicate, or detect objects.

d = v_water t / 2 m
Waves, Oscillations & Acoustics

Sonic Boom

An explosive impulsive acoustic thunderclap heard on the ground when an object travels faster than the speed of sound.

sin α = 1 / M (Mach Cone Angle) dB / Pa
Waves, Oscillations & Acoustics

Sound Intensity

The time-averaged rate of sound energy flow per unit area perpendicular to the direction of propagation.

I = P / A = p_rms² / (ρ v) W/m²
Astrophysics, Cosmology & Relativity

Spacetime Continuum

A 4D mathematical continuum combining 3D space and 1D time into a unified pseudo-Riemannian manifold.

ds² = g_μν dx^μ dx^ν (4D Pseudo-Riemannian Manifold) 4D Manifold (3 Space + 1 Time)
Nuclear & Particle Physics

Spark Chamber

A historic particle detector consisting of parallel metal plates filled with noble gas where high-voltage electrical sparks form along…

High Voltage Spark Discharge along Ionized Tracks Visual Spark Tracks