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As an example, water has a refractive index of 0.999 999 74 = 1 − 2.6 × 10 −7 for X-ray radiation at a photon energy of 30 keV (0.04 nm wavelength). [ 21 ] An example of a plasma with an index of refraction less than unity is Earth's ionosphere .
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. The coefficients are usually quoted for λ as the vacuum wavelength in micrometres. Usually, it is sufficient to use a two-term form of the ...
A. R. Forouhi and I. Bloomer deduced dispersion equations for the refractive index, n, and extinction coefficient, k, which were published in 1986 [1] and 1988. [2] The 1986 publication relates to amorphous materials, while the 1988 publication relates to crystalline.
In Cartesian coordinates (x, y, z), let the region y < 0 have refractive index n 1, intrinsic admittance Y 1, etc., and let the region y > 0 have refractive index n 2, intrinsic admittance Y 2, etc. Then the xz plane is the interface, and the y axis is normal to the interface (see diagram).
In a dispersive prism, material dispersion (a wavelength-dependent refractive index) causes different colors to refract at different angles, splitting white light into a spectrum. A compact fluorescent lamp seen through an Amici prism. Dispersion is the phenomenon in which the phase velocity of a wave depends on its frequency. [1]
Refractive index vs. wavelength for BK7 glass, showing measured points (blue crosses) and the Sellmeier equation (red line) Same as the graph above, but with Cauchy's equation (blue line) for comparison. While Cauchy's equation (blue line) deviates significantly from the measured refractive indices outside of the visible region (which is shaded ...
The Gaussian function has a 1/e 2 diameter (2w as used in the text) about 1.7 times the FWHM.. At a position z along the beam (measured from the focus), the spot size parameter w is given by a hyperbolic relation: [1] = + (), where [1] = is called the Rayleigh range as further discussed below, and is the refractive index of the medium.
The ratio v/λ is a constant equal to the frequency (ν) of the light, as is the quantized (photon) energy using the Planck constant and E = hν. Compared to the constant speed of light in vacuum (c), the index of refraction of water is n = c/v. The Gladstone–Dale term (n − 1) is the non-linear optical path length or time delay.