15Mar/100

## 3dB point & FWHM

When someone refers to the 3dB point of a graph, they are referring to the 50% point.  This can be explained through its derivation:

$10\cdot\log\left(\frac{1}{2}\right)\approx3d\!B$

Going forward with this definition, the Full Width Half Max (FWHM) of a figure is defined by the 3dB point.  To find the FWHM of a graph, you find the 2 points at which the graph crosses the half-max point (0.5 x peak's max value) - the horizontal distance between the two points is the FWHM.