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Refraction can give the impression that Earth's surface is flat, curved more convexly than it is, or even that it is concave (this is what happened in various trials of the Bedford Level experiment). The phenomenon of variable atmospheric bending can be seen when distant objects appear to be broken into pieces or even turned upside down.
Refraction of light at the interface between two media of different refractive indices, with n 2 > n 1.Since the phase velocity is lower in the second medium (v 2 < v 1), the angle of refraction θ 2 is less than the angle of incidence θ 1; that is, the ray in the higher-index medium is closer to the normal.
In atmospheric applications, refractivity is defined as N = n – 1, often rescaled as either [60] N = 10 6 (n – 1) [61] [62] or N = 10 8 (n – 1); [63] the multiplication factors are used because the refractive index for air, n deviates from unity by at most a few parts per ten thousand.
Snell's law (also known as the Snell–Descartes law, the ibn-Sahl law, [1] and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or air.
Refraction at interface. Many materials have a well-characterized refractive index, but these indices often depend strongly upon the frequency of light, causing optical dispersion. Standard refractive index measurements are taken at the "yellow doublet" sodium D line, with a wavelength (λ) of 589 nanometers.
The ratio of the refractive indices of the media determines the degree of refraction, and is summarized by Snell's law. Light of composite wavelengths (natural sunlight) disperses into a visible spectrum passing through a prism, because of the wavelength-dependent refractive index of the prism material ( dispersion ); that is, each component ...
The most general form of Cauchy's equation is = + + +,where n is the refractive index, λ is the wavelength, A, B, C, etc., are coefficients that can be determined for a material by fitting the equation to measured refractive indices at known wavelengths.
Patterns of seismic wave travel through Earth's mantle and core. S waves can not travel through the liquid outer core, so they leave a shadow on Earth's far side. P waves do travel through the core, but P wave refraction bends seismic waves away from P wave shadow zones.