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The refractive index of materials varies with the wavelength (and frequency) of light. [27] This is called dispersion and causes prisms and rainbows to divide white light into its constituent spectral colors. [28] As the refractive index varies with wavelength, so will the refraction angle as light goes from one material to another.
Refractive index: n = electromagnetism, optics (speed of light in vacuum over speed of light in a material) Transmittance: T = optics, spectroscopy (the ratio of the intensities of radiation exiting through and incident on a sample)
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.
Standard refractive index measurements are taken at the "yellow doublet" sodium D line, with a wavelength (λ) of 589 nanometers. There are also weaker dependencies on temperature , pressure / stress , etc., as well on precise material compositions (presence of dopants , etc.); for many materials and typical conditions, however, these ...
For step-index multimode fiber in a given medium, the acceptance angle is determined only by the indices of refraction of the core, the cladding, and the medium: =, where n is the refractive index of the medium around the fiber, n core is the refractive index of the fiber core, and n clad is the refractive index of the cladding.
A differential refractometer (DRI), or refractive index detector (RI or RID) is a detector that measures the refractive index of an analyte relative to the solvent. They are often used as detectors for high-performance liquid chromatography and size exclusion chromatography. They are considered to be universal detectors because they can detect ...
where denotes the phase difference due to each individual element, [3] and the fraction in parentheses is the electric polarizability as found from the refractive index using the Clausius–Mossotti relation. [4] Under the condition (n-1) << 1, this factor can be approximated as 2(n-1)/3.
The term p = 4πa(n − 1)/λ has as its physical meaning the phase delay of the wave passing through the centre of the sphere, where a is the sphere radius, n is the ratio of refractive indices inside and outside of the sphere, and λ the wavelength of the light. This set of equations was first described by van de Hulst in (1957). [5]