  By the means of the standard quantum mechanics formalism I present an
explicit derivation of the structure of power spectra in Danan {\em et al.} and
Zhou {\em et al.} experiments with nested dynamically changing Mach-Zehnder
interferometers. The analysis confirms that we observe prominent, first-order
peaks on frequencies related to some of the elements of the interferometer, but
not on others. However, as I shall demonstrate, there are also other, weaker
effects related to all relevant elements of the setup. In case of the Danan
{\em et al.} setup, there are even peaks at all frequencies of element
oscillations. When confronted in an experiment, these observations shall
challenge the interpretation of the experiments based on anomalous trajectories
of light.
