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Terms starting with P

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Waves, Oscillations & Acoustics

Phase Velocity

The speed at which a single monochromatic wave crest or phase front advances through a medium.

v_p = ω / k = f λ m/s Condensed Matter & Materials Physics

Phonon

A quantized collective vibrational wave excitation traveling through the periodic atomic or molecular lattice of a solid.

E = (n + ½) ℏ ω, p_crystal = ℏ q eV or J (Phonon Energy) Quantum & Atomic Physics

Phosphorescence

A type of photoluminescence where absorbed energy is emitted slowly over time due to spin-forbidden quantum transitions.

τ_phosphorescence ~ 10⁻³ s to hours Seconds to Hours (Lifetime) Quantum & Atomic Physics

Photoelectric Effect

The emission of electrons from a metal surface when light of frequency above a threshold value shines upon it.

K_max = h ν - Φ = e V_stopping eV or Joules Foundations of Physics

Physical Quantity

A quantifiable property of a physical system or phenomenon that can be measured and expressed as a numerical value multiplied by a unit.

Quantity = Value × Unit Various Mathematical & Computational Physics

Physical Simulation

The use of computer programs and numerical algorithms to simulate the time-dependent physical behavior of real-world or theoretical systems.

x(t + Δt) = x(t) + v(t) Δt + ½ a(t) Δt² Computational Modeling Condensed Matter & Materials Physics

Piezoelectric Effect

The generation of electric polarization charge in non-centrosymmetric crystals when subjected to mechanical stress (and vice versa).

Direct: P_i = d_ijk σ_jk; Reverse: ε_jk = d_ijk E_i C/N or m/V (Piezoelectric Coefficient d) Waves, Oscillations & Acoustics

Pitch

The subjective psychoacoustic perception of a sound's frequency by human listeners.

Pitch ∝ f Hz (or Musical Notes) Foundations of Physics

Planck's Constant

A fundamental physical constant that sets the scale for quantum mechanical phenomena, relating photon energy to its frequency.

E = hf, h = 6.62607015 × 10⁻³⁴ J·s J·s Quantum & Atomic Physics

Planck's Law & Blackbody Radiation

The foundational law describing the spectral radiance of electromagnetic radiation emitted by a blackbody in thermal equilibrium.

B_ν(T) = (2 h ν³ / c²) / (e^(h ν / (k_B T)) - 1), E = h ν W / (m²·sr·Hz) Plasma Physics

Plasma Antenna

A radiofrequency antenna that uses ionized plasma gas instead of solid metal conductors to transmit and receive electromagnetic signals.

Conductivity σ_p = (n_e e²) / (m_e (ν_coll - i ω)) MHz / GHz (RF Operating Frequency) Plasma Physics

Plasma Astrophysics

The branch of astrophysics applying plasma physics and magnetohydrodynamics to model cosmic phenomena throughout the universe.

B² / (2 μ₀) ~ ρ v² ~ P_thermal (Cosmic Equipartition) Cosmic Plasma Physics Plasma Physics

Plasma Beta

The ratio of kinetic thermal plasma pressure to magnetic field pressure in a magnetized plasma.

β = p_kinetic / p_magnetic = (n k_B T) / (B² / (2 μ₀)) Dimensionless Ratio Plasma Physics

Plasma Etching

A semiconductor manufacturing process using reactive gas plasmas to selectively remove surface layers from microchip wafers.

Anisotropic Reactive Ion Etching (RIE) nm/min (Etch Rate) & Aspect Ratio Plasma Physics

Plasma Frequency

The natural characteristic frequency of collective electrostatic electron oscillations in a plasma when perturbed from thermal equilibrium.

ω_pe = √(n_e e² / (m_e ε₀)) rad/s (Angular Frequency) Plasma Physics

Plasma Medicine

An emerging field of medical physics applying non-thermal atmospheric pressure plasmas directly to living tissues for therapeutic treatment.

RONS Generation: NO, O₂⁻, H₂O₂, OH•, ONOO⁻ Biomedical Application Plasma Physics

Plasma Parameter

A fundamental dimensionless number in plasma physics measuring the average number of electrons contained within a Debye sphere.

Λ = n_e λ_D³ ≫ 1 Dimensionless Number of Particles in Debye Sphere Plasma Physics

Plasma Sheath

A thin non-neutral positive boundary layer formed in a plasma adjacent to any physical wall or electrode.

V_sheath ≈ (k_B T_e / (2 e)) ln(m_i / (2 π m_e)), v_ion ≥ c_s = √(k_B T_e / m_i) V (Sheath Voltage) & m (Thickness ~ λ_D) Plasma Physics

Plasma Torch

An electromechanical device that generates a high-temperature thermal plasma jet by passing inert or reactive gas through an electric arc…

Thermal Equilibrium T_gas ≈ T_electron ~ 5,000–15,000 K kW to MW (Electrical Power Input) Plasma Physics

Plasma Wave Dispersion Relations

Mathematical equations relating wave frequency ω to wavevector k for electromagnetic and electrostatic waves propagating through magnetized…

CMA Diagram (Clemmow-Mullaly-Allis Wave Mode Classification) ω vs k (Dispersion Relation Curve) Geophysics & Environmental Physics

Plate Tectonics

The unifying geophysical theory stating that Earth's rigid outer lithosphere is divided into major tectonic plates drifting over the…

Plate Motion Velocity v_plate ~ 1–10 cm/year cm/year (Plate Drift Speed) Biophysics & Medical Physics

Poiseuille's Law of Blood Flow

A fluid dynamics equation governing laminar viscous fluid flow through a cylindrical vascular pipe.

Q = (π r⁴ ΔP) / (8 η L) m³/s or L/min (Volumetric Flow Rate) Mathematical & Computational Physics

Poisson Brackets

An algebraic operation between two phase space functions describing time evolution and conservation laws in Hamiltonian mechanics.

{f, g} = ∑ ((∂f / ∂q_i)(∂g / ∂p_i) - (∂f / ∂p_i)(∂g / ∂q_i)) Phase Space Operation Condensed Matter & Materials Physics

Poisson's Ratio

The ratio of transverse lateral strain to axial longitudinal strain in a material subjected to uniaxial stress.

ν = -ε_transverse / ε_axial = -(Δd / d₀) / (ΔL / L₀) Dimensionless Ratio (-1 to 0.5)