Experimental setup for the proof of electromagnetic waves in the style of Hertz

The structure corresponds to the mirror experiment conducted by Heinrich Hertz in 1888. There is a spark gap at the focal point of a metal mirror, and in the other a coherer serves as a receiver. The bundled electromagnetic waves of the transmitter change the conductivity of the receiver. Hertz was therefore able to show that the optical laws for his electromagnetic experiments were valid, and thus proved the wave nature postulated by Maxwell. The experiment also showed that waves "stretch out" across the space.