aaltoliike

Aaltoliike, or wave motion, refers to the propagation of a disturbance through a medium or through space, carrying energy and momentum without permanent displacement of the medium. In a wave, the disturbance varies in time and space, producing oscillations that travel as a wavefront.

Waves are broadly categorized as mechanical waves, which require a material medium, and electromagnetic waves, which can propagate in vacuum. Mechanical waves include sound in air, seismic waves in the Earth, surface waves on water, and elastic waves in solids. Electromagnetic waves include light, radio, and X-rays.

Key quantities: frequency f, wavelength λ, speed v, and amplitude A. The relation v = fλ connects these quantities. The wave equation describes the evolution of a wave field; for a simple one-dimensional case ∂^2ψ/∂t^2 = v^2 ∂^2ψ/∂x^2. Plane waves can be written ψ(x,t) = A cos(kx − ωt + φ) with k = 2π/λ and ω = 2πf. In electromagnetic waves, v equals the speed of light in the given medium (c in vacuum).

Phenomena include interference, diffraction, reflection, refraction, and polarization; the energy-carrying quantity can travel as a group velocity, while the phase velocity describes the phase progression. In linear media, waves obey the principle of superposition, allowing complex wave patterns to be constructed from simpler waves.

Aaltoliike is central in acoustics, optics, seismology, oceanography, and telecommunications. Its study traces to early modern science with contributors such as Hooke, Huygens, and Fresnel, and remains foundational in physics and engineering.