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842 terms · page 31 of 36

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Astrophysics, Cosmology & Relativity

Special Relativity

Albert Einstein's 1905 theory describing the physical behavior of space and time for observers moving in uniform non-accelerated inertial…

E² = (p c)² + (m₀ c²)², γ = 1 / √(1 - v²/c²) Theoretical Framework Geophysics & Environmental Physics

Specific Humidity

The mass ratio of water vapor contained within an air parcel relative to the total mass of the moist air parcel.

q = m_v / (m_v + m_d) ≈ 0.622 e / P g/kg (Grams of Water Vapor per kg of Air) Biophysics & Medical Physics

SPECT Scan

Single-Photon Emission Computed Tomography (SPECT), a nuclear medicine 3D functional imaging technique using gamma-emitting radioisotopes.

Gamma Camera 3D Tomographic Reconstruction MBq (Activity) & Hounsfield-like Functional Units Foundations of Physics

Speed of Light

The maximum speed at which all massless particles, electromagnetic waves, and information travel through a vacuum.

c = 299,792,458 m/s m/s Waves, Oscillations & Acoustics

Speed of Sound

The speed at which a pressure wave travels through an elastic medium.

v = √(K / ρ) (Fluids), v = √(γ R T / M) (Ideal Gas) m/s Optics

Spherical Aberration

An image blur defect in spherical lenses and mirrors where marginal rays focus closer to the element than paraxial central rays.

Δf_spherical = f_marginal - f_paraxial m Mathematical & Computational Physics

Spherical Harmonics

A set of special orthogonal functions defined on the 2D sphere surface serving as angular solutions to Laplace's equation in 3D spherical…

Y_l,m(θ, φ) = √(((2l+1)/(4π)) ((l-m)!/(l+m)!)) P_l^m(cos θ) e^(i m φ) Spherical Surface Functions Optics

Spherical Mirror

A curved mirror having a reflective surface shaped like a section of a sphere, classified as concave (converging) or convex (diverging).

1/f = 1/v + 1/u, f = R/2 m Condensed Matter & Materials Physics

Spin Glass

A disordered magnetic state characterized by random, competing ferromagnetic and antiferromagnetic interactions that freeze atomic spins…

Frustrated Exchange Interaction J_ij Disordered Magnetic Phase Quantum & Atomic Physics

Spin-Orbit Coupling

A relativistic quantum interaction between an electron's intrinsic spin magnetic moment and the internal magnetic field created by its…

H_SO = ξ(r) L · S eV (Energy Shift) Quantum & Atomic Physics

Spontaneous Emission

The process by which an excited atom or quantum system spontaneously decays to a lower energy state, emitting a photon of random phase and…

Rate = A₂₁ N₂ s⁻¹ (Transition Rate) Nuclear & Particle Physics

Spontaneous Symmetry Breaking

A physics phenomenon where the underlying mathematical equations of a system possess symmetry, but the ground state (vacuum) drops into a…

Vacuum Expectation Value ⟨0|φ|0⟩ = v ≠ 0 Energy VEV (GeV) Nuclear & Particle Physics

Standard Model

The theoretical physics framework classifying all known elementary particles and describing three fundamental forces: electromagnetism…

SU(3)_C × SU(2)_L × U(1)_Y Gauge Symmetry Theoretical Framework Waves, Oscillations & Acoustics

Standing Waves

A stationary wave pattern formed by the superposition of two identical waves traveling in opposite directions along the same medium.

y(x,t) = [2 A sin(k x)] cos(ω t) m Quantum & Atomic Physics

Stark Effect

The shifting and splitting of atomic spectral lines caused by the presence of an external static electric field.

ΔE = -p · E_ext (First-order: ΔE ∝ E_ext) eV (Energy Shift) Classical Mechanics

Static Equilibrium

The state of a rigid body where both net external force and net external torque are zero, keeping the body completely at rest.

∑ F = 0, ∑ τ = 0 N, N·m Mathematical & Computational Physics

Statistics and Probability

The mathematical frameworks for analyzing random phenomena, quantifying measurement uncertainty, and modeling ensemble behavior in…

P(A|B) = P(B|A) P(A) / P(B), μ = E[X], σ² = Var(X) Probability (0 to 1) Thermodynamics & Statistical Physics

Stefan-Boltzmann Law

The physical law asserting that total radiant power emitted per unit surface area of a blackbody is proportional to the fourth power of its…

E = σ T⁴, σ = 5.670374 × 10⁻⁸ W/(m²·K⁴) W/m² Astrophysics, Cosmology & Relativity

Stellar Nucleosynthesis

The collective nuclear fusion reactions inside stars that synthesize heavier chemical elements from lighter primordial hydrogen and helium.

3 α → ¹²C (Triple-Alpha Process at T ~ 10⁸ K) Nuclear Energy & Abundances Plasma Physics

Stellarator

A magnetic confinement fusion device that produces a helical magnetic field using complex, 3D non-planar external electromagnetic coils…

Rotational Transform ι = 1 / q (Generated entirely by 3D external coils) Dimensionless Magnetic Transform Quantum & Atomic Physics

Stern-Gerlach Experiment

A landmark 1922 experiment that proved space quantization and the intrinsic angular momentum (spin) of subatomic particles.

F_z = μ_z (∂B_z / ∂z), S_z = ± ℏ / 2 N (Force), J/T (Magnetic Moment) Quantum & Atomic Physics

Stimulated Emission

The process in which an incoming photon stimulates an excited atom to drop to a lower state, emitting a second identical photon.

Rate = B₂₁ ρ(ν) N₂ s⁻¹ (Transition Rate) Biophysics & Medical Physics

Stochastic vs Deterministic Radiation Effects

The classification of biological radiation damage into probability-driven stochastic risks (cancer) and threshold-driven deterministic…

Stochastic Probability P ∝ Dose; Deterministic Severity ∝ Dose (Threshold D_th) Risk Factor / Dose Threshold (Gy) Classical Mechanics

Stokes' Law

A mathematical law expressing viscous drag force experienced by small spherical particles moving at low speeds through a viscous fluid.

Fd = 6 π η r v N