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  2. Bessel's correction - Wikipedia

    en.wikipedia.org/wiki/Bessel's_correction

    Since the square root introduces bias, the terminology "uncorrected" and "corrected" is preferred for the standard deviation estimators: s n is the uncorrected sample standard deviation (i.e., without Bessel's correction) s is the corrected sample standard deviation (i.e., with Bessel's correction), which is less biased, but still biased

  3. Gamma correction - Wikipedia

    en.wikipedia.org/wiki/Gamma_correction

    Gamma correction or gamma is a nonlinear operation used to encode and decode luminance or tristimulus values in video or still image systems. [1] Gamma correction is, in the simplest cases, defined by the following power-law expression: =,

  4. Binoculars - Wikipedia

    en.wikipedia.org/wiki/Binoculars

    Porro prism designs have the added benefit of folding the optical path so that the physical length of the binoculars is less than the focal length of the objective. Porro prism binoculars were made in such a way to erect an image in a relatively small space, thus binoculars using prisms started in this way.

  5. Planck's law - Wikipedia

    en.wikipedia.org/wiki/Planck's_law

    This formula, apart from the first vacuum energy term, is a special case of the general formula for particles obeying Bose–Einstein statistics. Since there is no restriction on the total number of photons, the chemical potential is zero.

  6. Prismatic compass - Wikipedia

    en.wikipedia.org/wiki/Prismatic_compass

    Soldier using a prismatic compass to get an azimuth. A prismatic compass is a navigation and surveying instrument which is extensively used to find out the bearing of the traversing and included angles between them, waypoints (an endpoint of the course) and direction. [1]

  7. Riemann–Hurwitz formula - Wikipedia

    en.wikipedia.org/wiki/Riemann–Hurwitz_formula

    Indeed, to obtain this formula, remove disjoint disc neighborhoods of the branch points from S and their preimages in S' so that the restriction of is a covering. Removing a disc from a surface lowers its Euler characterstic by 1 by the formula for connected sum, so we finish by the formula for a non-ramified covering.

  8. Triangular prism - Wikipedia

    en.wikipedia.org/wiki/Triangular_prism

    In geometry, a triangular prism or trigonal prism [1] is a prism with 2 triangular bases. If the edges pair with each triangle's vertex and if they are perpendicular to the base, it is a right triangular prism. A right triangular prism may be both semiregular and uniform. The triangular prism can be used in constructing another polyhedron.

  9. Vertex distance - Wikipedia

    en.wikipedia.org/wiki/Vertex_distance

    Since most refractions (the measurement that determines the power of a corrective lens) are performed at a vertex distance of 12–14 mm, the power of the correction may need to be modified from the initial prescription so that light reaches the patient's eye with the same effective power that it did through the phoropter or trial frame. [1]