Physics
Articles about matter, energy, forces and physical laws.
Plum pudding model
Plum pudding model (Thomson's early atomic model)
Poisson's ratio
Polar moment of inertia
Polar moment of inertia (polar second moment of area)
Polarity
Polarity: physical and chemical orientation of opposing properties
Polarization
Polarization of Waves: Definition, Types, Causes, and Applications
Polypropylene
Polypropylene (PP)
Positron
Positron (antielectron): properties, behavior, and applications
Positronium
Potential
Potential energy
Pound (mass)
Pound (unit of mass)
Pound-force
Pound‑force (lbf): the imperial/US unit of force
Powder
Powder: definition, properties, production, uses and safety
Power (physics)
Power factor
Power spectrum
Pressure
Pressure (force per unit area)
Pressure is the amount of force applied perpendicular to a surface per unit area. It is fundamental in physics, engineering, meteorology and physiology, and is measured in pascals
Principle of relativity
Prism (optics)
Optical Prism: how it bends, splits and redirects light
Projectile
Projectile (physics, arms, and applications)
Proton decay
Proton decay: theory, predictions and experimental searches
Pseudovector
Pseudovector (Axial Vector): Definition, Properties, and Examples
QED
Quantum chromodynamics
Quantum electrodynamics
Quantum entanglement
Quantum entanglement: overview, history, and practical significance
Quantum fluctuation
Quantum foam
Quantum gravity
Quantum mechanics
Quantum mechanics: principles, history, and applications
Quantum state
Quantum state: definitions, representations, and significance
Quantum teleportation
Quantum teleportation: transferring quantum states using entanglement and classical channels
Quantum theory
Quantum tunnelling
Quark
Qubit
Qubit (quantum bit)
Radiation
Radiation: forms, history, uses, and safety
Radiation pressure
Force per area exerted by electromagnetic radiation; small for everyday light but important in astrophysics, laser physics, optical manipulation, and spacecraft propulsion.
Radio wave
Rankine scale
Rankine scale — the absolute temperature scale using Fahrenheit degrees
Rare-earth magnet
Rayleigh scattering
Elastic scattering of electromagnetic radiation by particles much smaller than the wavelength; explains blue skies, red sunsets, and wavelength-dependent attenuation in optics.
Réaumur scale
Réaumur temperature scale
Recoil
Refraction
Relative density
Relative density (ratio of densities)
Relativity
Resistance
Resistance: physical, biological, psychological, and social meanings