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The refractive index of electromagnetic radiation equals =, where ε r is the material's relative permittivity, and μ r is its relative permeability. [ 47 ] : 229 The refractive index is used for optics in Fresnel equations and Snell's law ; while the relative permittivity and permeability are used in Maxwell's equations and electronics.
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 Becke line test is a technique in optical mineralogy that helps determine the relative refractive index of two materials. It is done by lowering the stage (increasing the focal distance) of the petrographic microscope and observing which direction the light appears to move. This movement will always go into the material of higher refractive ...
Refraction of light at the interface between two media of different refractive indices, with n 2 > n 1.Since the 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.
Refractive index contrast, in an optical waveguide, such as an optical fiber, is a measure of the relative difference in refractive index of the core and cladding.The refractive index contrast, Δ, is often given by =, where n 1 is the maximum refractive index in the core (or simply the core index for a step-index profile) and n 2 is the refractive index of the cladding. [1]
The refractive index n of the gas can then be expressed in terms of the molar refractivity A as: n ≈ 1 + 3 A p R T {\displaystyle n\approx {\sqrt {1+{\frac {3Ap}{RT}}}}} where p is the pressure of the gas, R is the universal gas constant , and T is the (absolute) temperature, which together determine the number density N .
For common optical glasses, the refractive index calculated with the three-term Sellmeier equation deviates from the actual refractive index by less than 5×10 −6 over the wavelengths' range [5] of 365 nm to 2.3 μm, which is of the order of the homogeneity of a glass sample. [6]
In optics, Cauchy's transmission equation is an empirical relationship between the refractive index and wavelength of light for a particular transparent material. It is named for the mathematician Augustin-Louis Cauchy, who originally defined it in 1830 in his article "The refraction and reflection of light". [1]