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  2. Exponential decay - Wikipedia

    en.wikipedia.org/wiki/Exponential_decay

    Thus, the amount of material left is 21 = 1/2 raised to the (whole or fractional) number of half-lives that have passed. Thus, after 3 half-lives there will be 1/2 3 = 1/8 of the original material left. Therefore, the mean lifetime is equal to the half-life divided by the natural log of 2, or:

  3. Image sensor format - Wikipedia

    en.wikipedia.org/wiki/Image_sensor_format

    At one time only Nokia 808 PureView used a 1/1.2" sensor, almost three times the size of a 1/2.3" sensor. Bigger sensors have the advantage of better image quality, but with improvements in sensor technology, smaller sensors can achieve the feats of earlier larger sensors.

  4. 68–95–99.7 rule - Wikipedia

    en.wikipedia.org/wiki/68–95–99.7_rule

    In statistics, the 68–95–99.7 rule, also known as the empirical rule, and sometimes abbreviated 3sr, is a shorthand used to remember the percentage of values that lie within an interval estimate in a normal distribution: approximately 68%, 95%, and 99.7% of the values lie within one, two, and three standard deviations of the mean, respectively.

  5. Half-life - Wikipedia

    en.wikipedia.org/wiki/Half-life

    Half-life (symbol t½) is the time required for a quantity (of substance) to reduce to half of its initial value. The term is commonly used in nuclear physics to describe how quickly unstable atoms undergo radioactive decay or how long stable atoms survive. The term is also used more generally to characterize any type of exponential (or, rarely ...

  6. Percentage - Wikipedia

    en.wikipedia.org/wiki/Percentage

    Percentage. In mathematics, a percentage (from Latin per centum 'by a hundred') is a number or ratio expressed as a fraction of 100. It is often denoted using the percent sign (%), [1] although the abbreviations pct., pct, and sometimes pc are also used. [2] A percentage is a dimensionless number (pure number), primarily used for expressing ...

  7. Glossary of mathematical symbols - Wikipedia

    en.wikipedia.org/wiki/Glossary_of_mathematical...

    A mathematical symbol is a figure or a combination of figures that is used to represent a mathematical object, an action on mathematical objects, a relation between mathematical objects, or for structuring the other symbols that occur in a formula. As formulas are entirely constituted with symbols of various types, many symbols are needed for ...

  8. Repeating decimal - Wikipedia

    en.wikipedia.org/wiki/Repeating_decimal

    Every terminating decimal representation can be written as a decimal fraction, a fraction whose denominator is a power of 10 (e.g. 1.585 = ⁠ 1585 / 1000 ⁠); it may also be written as a ratio of the form ⁠ k / 2 n ·5 m ⁠ (e.g. 1.585 = ⁠ 317 / 2 3 ·5 2 ⁠).

  9. Radioactive decay - Wikipedia

    en.wikipedia.org/wiki/Radioactive_decay

    the half-life is related to the decay constant as follows: set N = N 0 /2 and t = T 1/2 to obtain t 1 / 2 = ln ⁡ 2 λ = τ ln ⁡ 2. {\displaystyle t_{1/2}={\frac {\ln 2}{\lambda }}=\tau \ln 2.} This relationship between the half-life and the decay constant shows that highly radioactive substances are quickly spent, while those that radiate ...