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The spectral hemispherical reflectance in frequency and spectral hemispherical reflectance in wavelength of a surface, denoted R ν and R λ respectively, are defined as [1] =,,, =,,, where Φ e, ν r is the spectral radiant flux in frequency reflected by that surface;
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.
In astrophysics and planetary science, spectral slope, also called spectral gradient, is a measure of dependence of the reflectance on the wavelength. In digital signal processing, it is a measure of how quickly the spectrum of an audio sound tails off towards the high frequencies, calculated using a linear regression. [1]
The plane of incidence is defined by the incoming radiation's propagation vector and the normal vector of the surface. There are two sets of Fresnel coefficients for two different linear polarization components of the incident wave.
Mathematically, for the spectral power distribution of a radiant exitance or irradiance one may write: =where M(λ) is the spectral irradiance (or exitance) of the light (SI units: W/m 2 = kg·m −1 ·s −3); Φ is the radiant flux of the source (SI unit: watt, W); A is the area over which the radiant flux is integrated (SI unit: square meter, m 2); and λ is the wavelength (SI unit: meter, m).
The transmittance or reflectance value for each wavelength of the test sample is then compared with the transmission or reflectance values from the reference sample. Most instruments will apply a logarithmic function to the linear transmittance ratio to calculate the 'absorbency' of the sample, a value which is proportional to the ...
Values of spectral parameters like reflectance can then be directly extracted from all pixels in the imagery, aggregated and averaged to produce a reflectance curve for spectral analysis. [ 6 ] [ 8 ] In terms of non-imaging spectroradiometry, data collection and sampling are usually conducted through direct scanning with spectroradiometers in ...
The degree of participation of each of these processes in the transmission is a function of the frequency, or wavelength, of the light, its polarization, and its angle of incidence. In general, reflection increases with increasing angle of incidence, and with increasing absorptivity at the boundary.