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  2. Optical path length - Wikipedia

    en.wikipedia.org/wiki/Optical_path_length

    A difference in OPL between two paths is often called the optical path difference (OPD). OPL and OPD are important because they determine the phase of the light and govern interference and diffraction of light as it propagates. In a medium of constant refractive index, n, the OPL for a path of geometrical length s is just

  3. Diffraction grating - Wikipedia

    en.wikipedia.org/wiki/Diffraction_grating

    The choice of + or – in the path difference formula depends on the sign convention for: plus if = describes the case of backscatter, minus if it describes specular reflection. Note that the pair of the black ray path parts and the pair of the light green ray path parts have no path difference in each pair, while there is a path difference in ...

  4. Fraunhofer diffraction - Wikipedia

    en.wikipedia.org/wiki/Fraunhofer_diffraction

    When the two waves are in phase, i.e. the path difference is equal to an integral number of wavelengths, the summed amplitude, and therefore the summed intensity is maximal, and when they are in anti-phase, i.e. the path difference is equal to half a wavelength, one and a half wavelengths, etc., then the two waves cancel, and the summed ...

  5. Bragg's law - Wikipedia

    en.wikipedia.org/wiki/Bragg's_law

    This path difference is (+) (′). The two separate waves will arrive at a point (infinitely far from these lattice planes) with the same phase , and hence undergo constructive interference , if and only if this path difference is equal to any integer value of the wavelength , i.e. n λ = ( A B + B C ) − ( A C ′ ) {\displaystyle n\lambda ...

  6. Free-space path loss - Wikipedia

    en.wikipedia.org/wiki/Free-space_path_loss

    Since this factor is not related to the radio wave path but comes from the receiving antenna, the term "free-space path loss" is a little misleading. Directivity of receiving antenna- while the above formulas are correct, the presence of Directivities Dt and Dr builds the wrong intuition in the FSPL Friis transmission formula. The formula seems ...

  7. Two-ray ground-reflection model - Wikipedia

    en.wikipedia.org/wiki/Two-ray_ground-reflection...

    From the figure the received line of sight component may be written as = {() /}and the ground reflected component may be written as = {() (+ ′) / + ′}where () is the transmitted signal, is the length of the direct line-of-sight (LOS) ray, + ′ is the length of the ground-reflected ray, is the combined antenna gain along the LOS path, is the combined antenna gain along the ground-reflected ...

  8. Snell's law - Wikipedia

    en.wikipedia.org/wiki/Snell's_law

    Snell's law (also known as the Snell–Descartes law, the ibn-Sahl law, [1] and the law of refraction) is a formula used to describe the relationship between the angles of incidence and refraction, when referring to light or other waves passing through a boundary between two different isotropic media, such as water, glass, or

  9. Optical path - Wikipedia

    en.wikipedia.org/wiki/Optical_path

    Optical path (OP) is the trajectory that a light ray follows as it propagates through an optical medium. The geometrical optical-path length or simply geometrical path length ( GPD ) is the length of a segment in a given OP, i.e., the Euclidean distance integrated along a ray between any two points. [ 1 ]