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The OPD can be calculated from the following equation: = where d 1 and d 2 are the distances of the ray passing through medium 1 or 2, n 1 is the greater refractive index (e.g., glass) and n 2 is the smaller refractive index (e.g., air).
These can generally be calculated from other equations if a fair amount of information is known about the chemical makeup of the star. From the definition, it is also clear that large optical depths correspond to higher rate of obscuration. Optical depth can therefore be thought of as the opacity of a medium.
The optical depth with respect to the height within the atmosphere is given by [3] = / and it follows that the total atmospheric optical depth is given by [3] = In both equations: k a is the absorption coefficient
penetration depth and skin depth; complex angular wavenumber and propagation constant; complex refractive index; complex electric permittivity; AC conductivity (susceptance). Note that in many of these cases there are multiple, conflicting definitions and conventions in common use. This article is not necessarily comprehensive or universal.
Penetration depth is a measure of how deep light or any electromagnetic radiation can penetrate into a material. It is defined as the depth at which the intensity of the radiation inside the material falls to 1/ e (about 37%) of its original value at (or more properly, just beneath) the surface.
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 gradient-index lens with a parabolic variation of refractive index (n) with radial distance (x). The lens focuses light in the same way as a conventional lens. If the refractive index of a medium is not constant but varies gradually with the position, the material is known as a gradient-index (GRIN) medium and is described by gradient index ...
Taking into account that a small angle expressed in radians can be approximated by its tangent, the formula to calculate stereoacuity dγ is this: = / (()) where a is the interocular separation of the observer, z the distance of the fixed peg from the eye and dz the position difference.