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  2. 4Pi microscope - Wikipedia

    en.wikipedia.org/wiki/4Pi_Microscope

    A 4Pi microscope is a laser scanning fluorescence microscope with an improved axial resolution.With it the typical range of the axial resolution of 500–700 nm can be improved to 100–150 nm, which corresponds to an almost spherical focal spot with 5–7 times less volume than that of standard confocal microscopy.

  3. Steradian - Wikipedia

    en.wikipedia.org/wiki/Steradian

    sr is the unit, steradian, sr = rad 2. Because the surface area A of a sphere is 4πr 2, the definition implies that a sphere subtends 4π steradians (≈ 12.56637 sr) at its centre, or that a steradian subtends 1/4π ≈ 0.07958 of a sphere. By the same argument, the maximum solid angle that can be subtended at any point is 4π sr.

  4. Surface area - Wikipedia

    en.wikipedia.org/wiki/Surface_area

    A sphere of radius r has surface area 4πr 2.. The surface area (symbol A) of a solid object is a measure of the total area that the surface of the object occupies. [1] The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc length of one-dimensional curves, or of the surface area for polyhedra (i.e., objects with ...

  5. List of mathematical constants - Wikipedia

    en.wikipedia.org/wiki/List_of_mathematical_constants

    A mathematical constant is a key number whose value is fixed by an unambiguous definition, often referred to by a symbol (e.g., an alphabet letter), or by mathematicians' names to facilitate using it across multiple mathematical problems. [1]

  6. 4Pi - Wikipedia

    en.wikipedia.org/wiki/4Pi

    IBM System/4 Pi, a family of avionics computers; 4Pi microscope, a microscope that uses interference and fluorescence computers; 4×π = 12.56637..., the solid angle of a complete sphere measured in steradians; Hermetic detector (also called a 4π detector)

  7. Fine-structure constant - Wikipedia

    en.wikipedia.org/wiki/Fine-structure_constant

    The absorption value for normal-incident light on graphene in vacuum would then be given by ⁠ πα / (1 + πα/2) 2 ⁠ or 2.24%, and the transmission by ⁠ 1 / (1 + πα/2) 2 ⁠ or 97.75% (experimentally observed to be between 97.6% and 97.8%). The reflection would then be given by ⁠ π 2 α 2 / 4 (1 + πα/2) 2 ⁠.

  8. List of formulae involving π - Wikipedia

    en.wikipedia.org/wiki/List_of_formulae_involving_π

    is the number of collisions made (in ideal conditions, perfectly elastic with no friction) by an object of mass m initially at rest between a fixed wall and another object of mass b 2N m, when struck by the other object. [1] (This gives the digits of π in base b up to N digits past the radix point.)

  9. AP Biology - Wikipedia

    en.wikipedia.org/wiki/AP_Biology

    Advanced Placement (AP) Biology (also known as AP Bio) is an Advanced Placement biology course and exam offered by the College Board in the United States. For the 2012–2013 school year, the College Board unveiled a new curriculum with a greater focus on "scientific practices".