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  2. Exponential decay - Wikipedia

    en.wikipedia.org/wiki/Exponential_decay

    This is the form of the equation that is most commonly used to describe exponential decay. Any one of decay constant, mean lifetime, or half-life is sufficient to characterise the decay. The notation λ for the decay constant is a remnant of the usual notation for an eigenvalue .

  3. 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 ...

  4. Time constant - Wikipedia

    en.wikipedia.org/wiki/Time_constant

    In physics and engineering, the time constant, usually denoted by the Greek letter τ (tau), is the parameter characterizing the response to a step input of a first-order, linear time-invariant (LTI) system. [1] [note 1] The time constant is the main characteristic unit of a first-order LTI system. In the time domain, the usual choice to ...

  5. Geometric progression - Wikipedia

    en.wikipedia.org/wiki/Geometric_progression

    The first block is a unit block and the dashed line represents the infinite sum of the sequence, a number that it will forever approach but never touch: 2, 3/2, and 4/3 respectively. A geometric progression, also known as a geometric sequence, is a mathematical sequence of non-zero numbers where each term after the first is found by multiplying ...

  6. Exponential growth - Wikipedia

    en.wikipedia.org/wiki/Exponential_growth

    The formula for exponential growth of a variable x at the growth rate r, ... If τ < 0 and b > 1, or τ > 0 and 0 < b < 1, then x has exponential decay. Example: ...

  7. Radioactive decay - Wikipedia

    en.wikipedia.org/wiki/Radioactive_decay

    t. e. Radioactive decay (also known as nuclear decay, radioactivity, radioactive disintegration, or nuclear disintegration) is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha, beta, and gamma decay.

  8. Doubling time - Wikipedia

    en.wikipedia.org/wiki/Doubling_time

    The doubling time is a characteristic unit (a natural unit of scale) for the exponential growth equation, and its converse for exponential decay is the half-life. As an example, Canada's net population growth was 2.7 percent in the year 2022, dividing 72 by 2.7 gives an approximate doubling time of about 27 years.

  9. Stretched exponential function - Wikipedia

    en.wikipedia.org/wiki/Stretched_exponential_function

    The stretched exponential function. is obtained by inserting a fractional power law into the exponential function. In most applications, it is meaningful only for arguments t between 0 and +∞. With β = 1, the usual exponential function is recovered. With a stretching exponent β between 0 and 1, the graph of log f versus t is ...