  The power spectrum of quantum fluctuations of the electromagnetic field
produced by an elementary particle is determined. It is found that in a wide
range of practically important frequencies the power spectrum of fluctuations
exhibits an inverse frequency dependence. The magnitude of fluctuations
produced by a conducting sample is shown to have a Gaussian distribution around
its mean value, and its dependence on the sample geometry is determined. In
particular, it is demonstrated that for geometrically similar samples the power
spectrum is inversely proportional to the sample volume. It is argued also that
the magnitude of fluctuations induced by external electric field is
proportional to the field strength squared. A comparison with experimental data
on flicker noise measurements in continuous metal films is made.
