Full width at half maximum

The half-value width of a function with a maximum, the difference between the two argument values ​​, for which the function values ​​are decreased to the half of the maximum, that is, the graphic " width at half-height ."

Accordingly, in English and in the art for the half-width of the label FWHM (Full Width at Half Maximum) is in use. If the function of the time -dependent, the abbreviation is FDHM (full duration at half maximum ) is used.

Definition

A function was at a maximum. At the positions, and the value of the function has decreased to the half of the maximum:

Then, the half-width is the difference.

Conversion

For a fixed functional form, one can convert the half-width defined in different widths of the function. So you can convert the FWHM and the standard deviation σ in one another eg during normal distribution:

Peak broadening

The increase in half- width of a peak is referred to as peak broadening. In most cases here, the intensity of the peak remains (that is, its integral over the expansion of size) the same and the peak height decreases. Possible causes of peak broadening for example, in physics, the line broadening (emission lines show energetic broadening ) and the dispersion ( wave packets dissolve over time).

Example of use

In the antenna technique of directivity of an antenna with " half-width of an antenna " (or " opening angle " ) is specified. Again, the specification of this angle is applied in the - 3dB limits. The half- width of the antenna in the example is thus 1.67 °