| Surface roughness
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- Most earth surface features lie somewhere between perfectly specular or perfectly diffuse reflectors. Whether a particular target reflects specularly or diffusely, or somewhere in between, depends on the surface roughness of the feature in comparison to the wavelength of the incoming radiation. If the wavelengths are much smaller than the surface variations or the particle sizes, diffuse reflection will dominate.
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| Rayleigh and modified Rayleigh criterion
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| A surface can
be characterized as rough or smooth using these criteria.
It classification upon the relationship between root mean
square (RMS) variation of surface undulation with respect
to a reference surface (h), wavelength (λ ) and the
angle of incidence (θ). It is given by the equation
presented here
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