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F number is a correlation number used in the analysis of polycyclic aromatic hydrocarbons (PAHs) as a descriptor of their hydrophobicity and molecular size. [1] It was proposed by Robert Hurtubise and co-workers in 1977.
[1] [2] [3] The f-number is also known as the focal ratio, f-ratio, or f-stop, and it is key in determining the depth of field, diffraction, and exposure of a photograph. [4] The f-number is dimensionless and is usually expressed using a lower-case hooked f with the format f / N , where N is the f-number.
Fluorine is a chemical element; it has symbol F and atomic number 9. It is the lightest halogen [ note 1 ] and exists at standard conditions as pale yellow diatomic gas. Fluorine is extremely reactive as it reacts with all other elements except for the light inert gases .
F = N A / 1/e = 9.648 533 212 331 001 84 × 10 4 C⋅mol −1. One common use of the Faraday constant is in electrolysis calculations. One can divide the amount of charge (the current integrated over time) by the Faraday constant in order to find the chemical amount of a substance (in moles) that has been electrolyzed.
In the periodic table of the elements, each column is a group. In chemistry, a group (also known as a family) [1] is a column of elements in the periodic table of the chemical elements. There are 18 numbered groups in the periodic table; the 14 f-block columns, between groups 2 and 3, are not numbered.
The f-number is the ratio of the lens's focal length to the diameter of the entrance pupil. F-number or F number also may refer to: F number (chemistry) , is a number that can be calculated for polycyclic aromatic hydrocarbons from their structure
The effective atomic number for electron interactions may be calculated with a similar approach. [ 5 ] [ 6 ] The cross-section based approach for determining Z eff is obviously much more complicated than the simple power-law approach described above, and this is why freely-available software has been developed for such calculations.
If the group is of the [ns, np] type, an amount of 0.85 from each electron with principal quantum number (n–1), and an amount of 1.00 for each electron with principal quantum number (n–2) or less. If the group is of the [d] or [f], type, an amount of 1.00 for each electron "closer" to the nucleus than the group.