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  2. Small-angle approximation - Wikipedia

    en.wikipedia.org/wiki/Small-angle_approximation

    The sine and tangent small-angle approximations are used in relation to the double-slit experiment or a diffraction grating to develop simplified equations like the following, where y is the distance of a fringe from the center of maximum light intensity, m is the order of the fringe, D is the distance between the slits and projection screen ...

  3. Numerical aperture - Wikipedia

    en.wikipedia.org/wiki/Numerical_aperture

    Due to Snell's law, the numerical aperture remains the same: NA = n 1 sin θ 1 = n 2 sin θ 2. In optics , the numerical aperture ( NA ) of an optical system is a dimensionless number that characterizes the range of angles over which the system can accept or emit light.

  4. Similarity measure - Wikipedia

    en.wikipedia.org/wiki/Similarity_measure

    In statistics and related fields, a similarity measure or similarity function or similarity metric is a real-valued function that quantifies the similarity between two objects. Although no single definition of a similarity exists, usually such measures are in some sense the inverse of distance metrics : they take on large values for similar ...

  5. Bounded function - Wikipedia

    en.wikipedia.org/wiki/Bounded_function

    A bounded operator: is not a bounded function in the sense of this page's definition (unless =), but has the weaker property of preserving boundedness; bounded sets are mapped to bounded sets (). This definition can be extended to any function f : X → Y {\displaystyle f:X\rightarrow Y} if X {\displaystyle X} and Y {\displaystyle Y} allow for ...

  6. Functional equation - Wikipedia

    en.wikipedia.org/wiki/Functional_equation

    For example, the gamma function is a function that satisfies the functional equation (+) = and the initial value () = There are many functions that satisfy these conditions, but the gamma function is the unique one that is meromorphic in the whole complex plane, and logarithmically convex for x real and positive ( Bohr–Mollerup theorem ).

  7. Window function - Wikipedia

    en.wikipedia.org/wiki/Window_function

    A popular window function, the Hann window. Most popular window functions are similar bell-shaped curves. In signal processing and statistics, a window function (also known as an apodization function or tapering function [1]) is a mathematical function that is zero-valued outside of some chosen interval. Typically, window functions are ...

  8. Natural logarithm of 2 - Wikipedia

    en.wikipedia.org/wiki/Natural_logarithm_of_2

    In a third layer, the logarithms of rational numbers r = ⁠ a / b ⁠ are computed with ln(r) = ln(a) − ln(b), and logarithms of roots via ln n √ c = ⁠ 1 / n ⁠ ln(c).. The logarithm of 2 is useful in the sense that the powers of 2 are rather densely distributed; finding powers 2 i close to powers b j of other numbers b is comparatively easy, and series representations of ln(b) are ...