Browse All 842 Physics Terms A–Z

Miller Indices Condensed Matter & Materials Physics Dimensionless Notation System A standardized three-integer crystallographic notation system (h k l) used to specify direction vectors and orientation of planes in a crystal lattice. (h k l) = Reciprocals of lattice axis intercepts

Minimum Deviation Optics Degrees (°) The minimum value of deviation angle achieved when light passes symmetrically through a triangular prism. n = sin[(A + δ_m)/2] / sin(A/2)

Minkowski Space Astrophysics, Cosmology & Relativity Flat 4D Spacetime Metric The flat four-dimensional spacetime manifold combining 3D Euclidean space and time used to formulate Special Relativity. ds² = -c² dt² + dx² + dy² + dz²

Mirage Optics N/A An optical illusion caused by continuous refraction of light rays passing through air layers with steep temperature and density gradients. n(z) = f(Temperature gradient)

Molar Heat Capacity Thermodynamics & Statistical Physics J/(mol·K) The heat energy required to raise the temperature of one mole of a substance by one Kelvin. C_m = Q / (n ΔT), C_p - C_v = R

Mole Foundations of Physics mol The SI base unit for amount of substance, containing exactly 6.02214076 × 10²³ elementary entities. n = m / M = N / Na

Molecular Dynamics Mathematical & Computational Physics Atomic Trajectory Simulation A computer simulation method for analyzing the physical movements of atoms and molecules by numerically integrating Newton's equations of motion. m_i d²r_i/dt² = F_i = -∇_i V(r₁, r₂, ..., r_N)

Molecular Motors Biophysics & Medical Physics pN (Piconewtons) & nm (Step Length) Protein-based molecular machines that convert chemical energy from ATP hydrolysis into mechanical work and linear movement. F_step ≈ 6 pN, Step Size d ≈ 8 nm (Kinesin on Microtubule)

Moment of Inertia Classical Mechanics kg·m² A quantitative measure of a body's rotational inertia - its resistance to changes in rotational motion about a given axis. I = ∑ m_i r_i² = ∫ r² dm

Momentum Classical Mechanics kg·m/s A fundamental vector quantity equal to the product of an object's mass and its velocity, representing its quantity of motion. p = m v

Monte Carlo Method Mathematical & Computational Physics Stochastic Numerical Method A class of computational algorithms that rely on repeated random sampling to obtain numerical solutions for complex physical systems. I ≈ (1 / N) ∑_(i=1)^(N) f(X_i) (Central Limit Theorem)

Moseley's Law Quantum & Atomic Physics Hz^(1/2) (Frequency Square Root) An empirical law establishing a linear relationship between the square root of characteristic X-ray frequency emitted by an atom and its atomic number Z. √ν = A (Z - b)

MOSFET Electromagnetism & Electronics A (Current) A Metal-Oxide-Semiconductor Field-Effect Transistor that uses an insulated gate voltage to control current flow through an underlying semiconductor channel. I_D = ½ μ_n C_ox (W/L) (V_GS - V_th)²

Most Probable Speed Thermodynamics & Statistical Physics m/s The particle speed corresponding to the maximum peak of the Maxwell-Boltzmann speed distribution curve. v_mp = √(2 kB T / m) = √(2 R T / M)

Moving Coil Galvanometer, Ammeter & Voltmeter Electromagnetism & Electronics A (Current), V (Voltage) An electromechanical instrument that measures small currents using magnetic torque on a pivoted coil, converted to an ammeter or voltmeter using shunts or series resistors. τ = N I A B = k θ; Ammeter: S = I_g G / (I - I_g); Voltmeter: R_s = (V / I_g) - G

Multiverse Astrophysics, Cosmology & Relativity Cosmological Hypothesis A hypothetical set of multiple co-existing universes that together comprise all of physical reality. Cosmic Inflation Bubble Universes & Many-Worlds Everett Branching

Muon Nuclear & Particle Physics MeV/c² (Mass Energy) A second-generation elementary charged lepton with a mass approximately 207 times greater than an electron. m_μ ≈ 105.66 MeV/c², τ_μ ≈ 2.2 μs, Spin = ½

Mutual Inductance Electromagnetism & Electronics H (Henries) The induction of an electromotive force in a secondary circuit loop caused by a time-varying current in an adjacent primary circuit loop. E₂ = -M (dI₁/dt), M = k √(L₁ L₂)

N-type Semiconductor Condensed Matter & Materials Physics cm⁻³ (Electron Concentration) An extrinsic semiconductor in which pentavalent donor impurities create an excess concentration of free electrons as majority charge carriers. n ≈ N_D ≫ p, n p = n_i²

Nanomedicine Biophysics & Medical Physics nm (Nanoparticle Diameter ~10–100 nm) The medical application of nanotechnology utilizing engineered nanoparticles for disease diagnosis, targeted drug delivery, and therapy. EPR Effect: Enhanced Permeability and Retention in Tumors

Near Point & Far Point Optics m (or cm) The closest and farthest distances at which the human eye can focus objects sharply on the retina. Near Point ≈ 25 cm (Normal adult eye), Far Point = ∞

Nebula Astrophysics, Cosmology & Relativity Light-Years (Diameter) An interstellar cloud of dust, hydrogen, helium, and ionized gases in space, serving as a site for star formation. M_Jeans = (5 k_B T / (G μ m_H))^(3/2) (3 / (4 π ρ))^(1/2)

Nernst Equation in Biophysics Biophysics & Medical Physics mV (Equilibrium Potential) An equation calculating the exact electrical equilibrium potential across a membrane permeable to a single ion species. E_ion = (R T / (z F)) ln([Ion]_out / [Ion]_in)

Neurophysics Biophysics & Medical Physics Biophysical Neural Network Model The interdisciplinary field applying physical principles and non-linear mathematical modeling to study nervous system function. Hodgkin-Huxley Model: C_m (dV/dt) = I_ext - g_Na m³ h (V-E_Na) - g_K n⁴ (V-E_K) - g_L (V-E_L)

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