V.2 No 1

7

Transversal acoustic wave in gas

2. Experimental device

2.1 General scheme of the experiment

As we know (see e.g. [11, pp. 23- 24]), the transverseness of EM waves is effectively corroborated by the experiments on the microwave systems. “Let the receiver of radiation be a trumpet oriented in a definite way and connected with the crystal detector and the waveguide. Note that such system transmits the electromagnetic wave of quite definite oscillation direction (with the definite linear polarisation). When turning the radiator (klystron) by /2 relatively to the receiver, we observe the signal completely vanishing. This experiment illustrates that the klystron radiates a linearly polarised electromagnetic wave (if the radiation was not polarised, then the turning by /2 must not reflect on the signal magnitude). But at the same time it evidences that the longitudinal component of an electromagnetic wave is absent, because otherwise it would be impossible to damp it out by turning the source or receiver in the plane normal to the wave propagation direction” [11, p. 23- 24]. With it we should mark that “at definite conditions of an experiment there can arise a complicated pattern whose interpretation can easy be mistaken. We mean the wave propagation when there are present some restricting baffles, reflectors and other alike devices” [11, p. 24].

Fig.3. General scheme of experimental set radiating/ receiving the transverse acoustic wave in gas medium

To register the transversal acoustic wave in gas, the experimental circuit described above and shown in Fig. 3 was taken as the basis. In this circuit, the electrical sinusoidal oscillations of the generator 1 excited the acoustic wave source 2 developed specially for this experiment. They were received by the special receiver of transversal acoustic waves 3 whose construction was completely identical to those of radiator. The received signal was built up by the amplifier 5 and registered by the cathode-ray oscillograph 6 working in the slave sweep regime of the generator 1. This last was necessary to measure the phase characteristics of the radiation/reception of a transversal acoustic wave. To make the wave directed and to avoid the distortions caused by the spurious reflection, both the radiator and receiver were placed into the special trumpets 4.