Physics terms starting with N

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)

Neutral Beam Injection (NBI) Plasma Physics MW (Beam Power) & keV (Particle Energy ~100–1000 keV) A primary plasma heating and current drive method where high-energy neutral atom beams are injected into a magnetic confinement fusion reactor. P_NBI = I_beam × V_acceleration

Neutrino Nuclear & Particle Physics eV/c² (Mass Limit) An extremely light, electrically neutral spin-1/2 elementary lepton that interacts almost exclusively via the weak nuclear force. m_ν < 0.1 eV/c², Spin = ½, Charge = 0

Neutrino Oscillations Nuclear & Particle Physics Probability (0 to 1) A quantum mechanical phenomenon in which a neutrino created with a specific lepton flavor changes flavor as it propagates through space. P(ν_α → ν_β) = sin²(2θ) sin²(1.27 Δm² L / E)

Neutron Star Astrophysics, Cosmology & Relativity M_☉ (Mass), km (Radius) An ultradense stellar core remnant produced by the core-collapse supernova explosion of a massive star, composed almost entirely of neutrons. M ≈ 1.4–2.1 M_☉, R ≈ 10–12 km, ρ ≈ 10¹⁷ kg/m³

Newton's First Law Classical Mechanics N/A The principle that an object remains at rest or continues in uniform motion in a straight line unless acted upon by a net external force. ∑ F = 0 ⇒ v = constant

Newton's Rings Optics m An interference pattern of concentric bright and dark rings formed by an air film enclosed between a plano-convex lens and a flat glass plate. r_m² = m λ R (Dark rings in reflection)

Newton's Second Law Classical Mechanics N The law stating that net force acting on a body equals the rate of change of its linear momentum, simplified to mass times acceleration for constant mass. F_net = m a

Newton's Third Law Classical Mechanics N The law stating that whenever two objects interact, they exert forces on each other that are equal in magnitude and opposite in direction. F_A_to_B = -F_B_to_A

Nodes & Antinodes Waves, Oscillations & Acoustics m Specific fixed positions on a standing wave where displacement amplitude is zero (nodes) or maximum (antinodes). Node Spacing = λ / 2, Antinode Spacing = λ / 2

Non-conservative Force Classical Mechanics N A force for which work done depends on the specific path taken, dissipating mechanical energy into heat, sound, or internal energy. W_non-cons = ΔME = ΔKE + ΔPE

Non-linear Oscillations Waves, Oscillations & Acoustics Various Oscillatory systems where restoring forces do not obey linear Hooke's law, leading to amplitude-dependent frequency and chaotic behavior. m (d²x/dt²) + k x + β x³ = 0 (Duffing Equation)

Non-Neutral Plasma Plasma Physics Single-Species Charged Cloud A plasma composed exclusively of a single species of charged particles (electrons, positrons, or single ions) without background charge neutralization. n_e ≫ n_i (Pure Electron or Ion Plasma)

Non-Newtonian Fluids Condensed Matter & Materials Physics Pa·s (Apparent Viscosity η) Fluids whose shear viscosity changes depending on applied shear rate, stress magnitude, or shear history. τ = K (du / dy)^n (n ≠ 1)

Nonlinear Dynamics Mathematical & Computational Physics Phase Space Dynamics The study of physical systems governed by non-linear equations where output changes are not directly proportional to input changes. d x / dt = f(x) (where f is non-linear)

Normal Force Classical Mechanics N The perpendicular contact force exerted by a surface on an object pressing against it. N = m g cos θ

Normal Modes Waves, Oscillations & Acoustics Hz Characteristic independent natural patterns of motion in which all parts of an oscillating system move sinusoidally at the same natural frequency. f_n = n f1 = n v / (2 L)

Nuclear Binding Energy Nuclear & Particle Physics MeV (Mega-electronvolts) The minimum energy required to completely disassemble an atomic nucleus into its constituent protons and neutrons. E_b = Δm c² = [Z m_p + (A - Z) m_n - M_nucleus] c²

Nuclear Fission Nuclear & Particle Physics MeV (Mega-electronvolts) A nuclear reaction in which a heavy nucleus splits into two or more smaller daughter nuclei accompanied by the release of neutrons and substantial energy. ¹₀n + ²³⁵₉₂U → ²³⁶₉₂U* → ¹⁴¹₅₆Ba + ⁹²₃₆Kr + 3 ¹₀n + Q (~200 MeV)

Terms starting with N