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842 terms · page 1 of 36
Absolute Uncertainty
The margin of measurement error expressed in the same physical units as the quantity being measured.
Foundations of PhysicsAbsolute Zero
The theoretical lower limit of thermodynamic temperature, defined as 0 Kelvin (-273.15°C or -459.67°F).
Biophysics & Medical PhysicsAbsorbed Dose
The physical quantity measuring the amount of energy deposited by ionizing radiation per unit mass of matter.
Waves, Oscillations & AcousticsAbsorption Coefficient
The fraction of incident sound energy absorbed by a material surface rather than reflected.
Classical MechanicsAcceleration
The vector rate of change of velocity with respect to time.
OpticsAcceptance Angle
The maximum angle relative to the fiber axis at which incident light can enter the fiber core and undergo total internal reflection.
OpticsAccommodation of the Eye
The automatic adjustment process by which ciliary muscles alter crystalline lens focal length to focus objects at varying distances onto…
Astrophysics, Cosmology & RelativityAccretion Disk
A rotating disk structure formed by infalling diffuse matter orbiting a massive central body like a white dwarf, neutron star, or black…
Foundations of PhysicsAccuracy
The degree of closeness of a measured value or experimental result to the true or accepted reference value.
Waves, Oscillations & AcousticsAcoustic Impedance
The physical opposition offered by a medium to sound wave flow, defined as ratio of acoustic pressure to particle velocity.
Waves, Oscillations & AcousticsAcoustic Power
The total sound energy emitted by an acoustic source per unit time in all directions.
Waves, Oscillations & AcousticsAcoustic Resonance
The amplification of sound waves within a hollow cavity or tube when driven at frequencies matching cavity standing wave modes.
Biophysics & Medical PhysicsAction Potential
A rapid, self-propagating electrical voltage impulse along the membrane of excitable cells (neurons and muscle cells).
Biophysics & Medical PhysicsActive Transport
The energy-requiring transport of ions or molecules across a biological cell membrane against their concentration gradient.
Geophysics & Environmental PhysicsAdiabatic Lapse Rate
The rate at which the temperature of a rising or descending air parcel changes as it expands or compresses adiabatically without heat…
Thermodynamics & Statistical PhysicsAdiabatic Process
A thermodynamic process in which no heat is transferred into or out of the system.
Biophysics & Medical PhysicsALARA Principle
A fundamental radiation protection safety principle stating that all radiation exposures must be kept 'As Low As Reasonably Achievable'…
Geophysics & Environmental PhysicsAlbedo
The fraction of total incident solar electromagnetic radiation reflected back into space by a surface or planetary body.
Plasma PhysicsAlfvén Wave
A fundamental magnetohydrodynamic (MHD) wave in which ions in a magnetized plasma oscillate in response to magnetic field line tension.
Mathematical & Computational PhysicsAlgorithm
A finite, unambiguous sequence of mathematical instructions implemented in software to solve specific physical equations or compute…
Condensed Matter & Materials PhysicsAllotropy
The property of a chemical element to exist in two or more distinct structural forms in the same physical state.
Condensed Matter & Materials PhysicsAlloying
The process of melting and combining a primary metal with additional metallic or non-metallic elements to create a material with enhanced…
Nuclear & Particle PhysicsAlpha Decay
A radioactive decay process in which an unstable heavy nucleus emits an alpha particle (Helium-4 nucleus, ⁴₂He²⁺).
Condensed Matter & Materials PhysicsAmorphous Solid
A non-crystalline solid lacking long-range periodic atomic translational order.