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This is a list of well-known dimensionless quantities illustrating their variety of forms and applications. The tables also include pure numbers, dimensionless ratios, or dimensionless physical constants; these topics are discussed in the article.
Physics relies on dimensionless numbers like the Reynolds number in fluid dynamics, [6] the fine-structure constant in quantum mechanics, [7] and the Lorentz factor in relativity. [8] In chemistry, state properties and ratios such as mole fractions concentration ratios are dimensionless. [9]
Download as PDF; Printable version; In other projects ... With reference to the Buckingham π theorem there are 9 – 5 = 4 dimensionless groups. ... James R. (1976).
Download as PDF; Printable version; In other projects ... Pages in category "Dimensionless quantities" The following 9 pages are in this category, out of 9 total ...
In spectroscopy, oscillator strength is a dimensionless quantity that expresses the probability of absorption or emission of electromagnetic radiation in transitions between energy levels of an atom or molecule. [1] [2] For example, if an emissive state has a small oscillator strength, nonradiative decay will outpace radiative decay.
In some cases, a Planck unit may suggest a limit to a range of a physical quantity where present-day theories of physics apply. [19] For example, our understanding of the Big Bang does not extend to the Planck epoch , i.e., when the universe was less than one Planck time old.
A meaningful test on the time-variation of G would require comparison with a non-gravitational force to obtain a dimensionless quantity, e.g. through the ratio of the gravitational force to the electrostatic force between two electrons, which in turn is related to the dimensionless fine-structure constant.
In fluid dynamics, the capillary number (Ca) is a dimensionless quantity representing the relative effect of viscous drag forces versus surface tension forces acting across an interface between a liquid and a gas, or between two immiscible liquids.