Direct electrodynamic electromagnetic-acoustic transformation in a normal polarizing field: I. Dependence on the gap according to the spectral theory

The dependences of the amplitude and directivity characteristics of shear vibrations on the gap between a transmitter of a high-frequency field and the boundary of a conducting half-space are calculated with the use of the theoretical description of the electromagnetic-acoustic transformation obtained earlier. It is shown that the geometry of the transmitter—the distance from its center to the center of the emitting element—plays an important role in the formation of these dependences. The size determines the approximate limits of the most efficient part of the spectrum of the projections of the wave vectors along the interface between media, i.e., the part that forms the studied dependences. It is revealed that these limits are substantially affected by the external-field frequency, which, in addition to the geometry of the transmitter, is a specific factor that controls the limits of the spectrum. The obtained dependences turn out to be less steep than those derived on the basis of a frequency-independent harmonic theory.