Refraktio

Refraktio (refraction) is a wave phenomenon where the direction of propagation changes when passing across a boundary between media with different propagation speeds. This occurs for light, sound, water waves and other waves; in optics it describes light bending when crossing interfaces.

Speed and wavelength: light's speed is slower in a denser medium; the frequency remains constant; the wavelength adjusts according to n = c/v, lambda = lambda0 / n.

Snell's law: n1 sin(theta1) = n2 sin(theta2); explains bending. If n2 > n1, ray bends toward the normal; if n2 < n1, away from the normal.

Dispersion: refractive index depends on wavelength; different colors bend by different amounts; prisms and optical fibers rely on this effect; materials may be described by Sellmeier equations.

Boundary interactions: partial reflection and transmission described by Fresnel equations; total internal reflection occurs for incidence above the critical angle when light goes from higher to lower index; this principle is fundamental to fiber optics and many optical devices.

Natural phenomena and applications: atmospheric refraction causes the Sun and stars to appear higher in the sky near the horizon; mirages are another example. In technology, refraktio underpins lenses in glasses, cameras and microscopes, as well as waveguides and fiber-optic communication.