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
Snell's law: n1 sin(theta1) = n2 sin(theta2); explains bending. If n2 > n1, ray bends toward the normal;
Dispersion: refractive index depends on wavelength; different colors bend by different amounts; prisms and optical fibers
Boundary interactions: partial reflection and transmission described by Fresnel equations; total internal reflection occurs for incidence
Natural phenomena and applications: atmospheric refraction causes the Sun and stars to appear higher in the