Physics terms starting with L

Light Year Astrophysics, Cosmology & Relativity Light-Years (ly) An astronomical unit of length equal to the distance light travels in a vacuum in one Julian year (365.25 days). 1 ly = c × 1 year ≈ 9.461 × 10¹⁵ m ≈ 63,241 AU

Linear Algebra Mathematical & Computational Physics Vector Spaces & Matrices The mathematical discipline studying vector spaces, linear transformations, matrices, and systems of linear equations. A x = b, v · w = ∑ v_i w_i

Linear Energy Transfer (LET) Biophysics & Medical Physics keV/μm (Kiloelectronvolts per micrometer) A measure of the rate at which an ionizing radiation particle deposits ionization energy along its path length through biological tissue. LET = dE / dx

Linear Thermal Expansion Thermodynamics & Statistical Physics K⁻¹ (°C⁻¹) The fractional change in length of a solid material per degree change in temperature. ΔL = α L0 ΔT

Liquid Crystals Condensed Matter & Materials Physics Dimensionless Orientational Order S States of matter possessing physical properties intermediate between conventional isotropic liquids and ordered crystalline solids. Nematic Order Parameter S = ½ ⟨3 cos² θ - 1⟩

Liquid Drop Model Nuclear & Particle Physics MeV (Binding Energy Calculation) A classical nuclear model treating the atomic nucleus as an incompressible liquid droplet of dense nuclear fluid bound by short-range nuclear forces. E_b = a_v A - a_s A^(2/3) - a_c Z²/A^(1/3) - a_a (A-2Z)²/A + δ

Lissajous Figures Waves, Oscillations & Acoustics N/A Complex geometric curves traced by combining two perpendicular simple harmonic oscillations. x(t) = A sin(a t + δ), y(t) = B sin(b t)

Lithosphere Geophysics & Environmental Physics km (Lithospheric Thickness) The rigid, brittle outermost mechanical shell of Earth comprising the entire crust and uppermost solid mantle. Elastic Thickness h_e ~ 10–200 km

Local Group Astrophysics, Cosmology & Relativity Megaparsecs (Mpc) The small galaxy cluster group comprising the Milky Way, Andromeda (M31), Triangulum (M33), and over 80 dwarf satellite galaxies. Diameter ~ 3 Mpc (~10 million ly), Mass ~ 2 × 10¹² M_☉

Logic Gates Electromagnetism & Electronics Binary (0 or 1) Elementary digital electronic building blocks that perform Boolean logical operations on one or more binary inputs to yield a single binary output. AND: Y = A·B; OR: Y = A + B; NOT: Y = Ā; NAND: Y = (A·B)̄

Longitudinal Wave Waves, Oscillations & Acoustics m A wave in which medium particles oscillate parallel to the direction of wave energy propagation. s(x,t) = s_max cos(k x - ω t)

Lorentz Factor Astrophysics, Cosmology & Relativity Dimensionless Factor (γ ≥ 1) The fundamental relativistic factor by which time dilation, length contraction, and relativistic mass scale for objects moving at velocity v. γ = 1 / √(1 - v²/c²) = 1 / √(1 - β²)

Lorentz Force Electromagnetism & Electronics N (Newtons) The combined force exerted on a charged particle moving through electromagnetic fields containing both electric and magnetic field components. F = q (E + v × B)

Loudness Waves, Oscillations & Acoustics Sone (or Phon) The subjective human psychological sensation of sound strength, depending on physical intensity and ear frequency response. Loudness ∝ log10(I / I0)

Luminous Flux Optics Lumens (lm) A photometric quantity measuring total perceived power of light emitted by a source, weighted by human eye spectral sensitivity. Φ_v = 683 ∫ P(λ) V(λ) dλ

Lyman Series Quantum & Atomic Physics Ultraviolet Wavelengths (nm) The hydrogen spectral series resulting from electron transitions dropping from higher excited states down to the ground state (n=1). 1 / λ = R_H (1 / 1² - 1 / n_i²), n_i = 2, 3, 4...

Terms starting with L