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  2. Decibel - Wikipedia

    en.wikipedia.org/wiki/Decibel

    The decibel originates from methods used to quantify signal loss in telegraph and telephone circuits. Until the mid-1920s, the unit for loss was miles of standard cable (MSC). 1 MSC corresponded to the loss of power over one mile (approximately 1.6 km) of standard telephone cable at a frequency of 5000 radians per second (795.8 Hz), and matched closely the smallest attenuation detectable to a ...

  3. Orders of magnitude (length) - Wikipedia

    en.wikipedia.org/wiki/Orders_of_magnitude_(length)

    1.6 × 10 −5 quectometers (1.6 × 10 −35 meters) – the Planck length (Measures of distance shorter than this do not make physical sense, according to current theories of physics.) 1 qm – 1 quectometer, the smallest named subdivision of the meter in the SI base unit of length, one nonillionth of a meter.

  4. Parts-per notation - Wikipedia

    en.wikipedia.org/wiki/Parts-per_notation

    In fractions like "2 nanometers per meter" (2 n m / m = 2 nano = 2×10 −9 = 2 ppb = 2 × 0.000 000 001), so the quotients are pure-number coefficients with positive values less than or equal to 1. When parts-per notations, including the percent symbol (%), are used in regular prose (as opposed to mathematical expressions), they are still pure ...

  5. ISO metric screw thread - Wikipedia

    en.wikipedia.org/wiki/ISO_metric_screw_thread

    A metric ISO screw thread is designated by the letter M followed by the value of the nominal diameter D (the maximum thread diameter) and the pitch P, both expressed in millimetres and separated by a dash or sometimes the multiplication sign, × (e.g. M8-1.25 or M8×1.25). If the pitch is the normally used "coarse" pitch listed in ISO 261 or ...

  6. f-number - Wikipedia

    en.wikipedia.org/wiki/F-number

    Since real lenses have transmittances of less than 100%, a lens's T-stop number is always greater than its f-number. [10] With 8% loss per air-glass surface on lenses without coating, multicoating of lenses is the key in lens design to decrease transmittance losses of lenses. Some reviews of lenses do measure the T-stop or transmission rate in ...

  7. List of countries by Human Development Index - Wikipedia

    en.wikipedia.org/wiki/List_of_countries_by_Human...

    This is an accepted version of this page This is the latest accepted revision, reviewed on 11 December 2024. World map of countries or territories by Human Development Index scores in increments of 0.050 (based on 2022 data, published in 2024) ≥ 0.950 0.900–0.950 0.850–0.899 0.800–0.849 0.750–0.799 0.700–0.749 0.650–0.699 0.600–0.649 0.550–0.599 0.500–0.549 0.450–0.499 0. ...

  8. List of countries by life expectancy - Wikipedia

    en.wikipedia.org/wiki/List_of_countries_by_life...

    This list of countries by life expectancy provides a comprehensive list of countries alongside their respective life expectancy figures. The data is differentiated by sex, presenting life expectancies for males, females, and a combined average.

  9. List of countries by government budget - Wikipedia

    en.wikipedia.org/wiki/List_of_countries_by...

    Normalizing the data, by dividing the budget balance by GDP, enables easy comparisons across countries and indicates whether a national government saves or borrows money. Countries with high budget deficits (relative to their GDPs) generally have more difficulty raising funds to finance expenditures, than those with lower deficits." [12]