• Tags: Hertz, experimental, verification
• Difficulty: Foundation

Heinrich Hertz (1887) first experimentally demonstrated EM waves, confirming Maxwell's prediction. His setup: an induction coil produced sparks across a gap in a transmitter circuit (an LC oscillator), generating EM waves. A receiver loop with a small gap, placed several meters away, showed tiny sparks — proving the waves had traveled through space. Hertz demonstrated that EM waves: (1) travel at the speed of light, (2) can be reflected (metal sheets), (3) can be refracted (prisms of pitch), (4) can be polarized (wire grids), (5) show interference and diffraction. These are all properties of light, confirming Maxwell's insight that light itself is an EM wave. Hertz's transmitter frequency was ~100 MHz (wavelength ~3 m). The unit of frequency (Hz) is named after him. Marconi later developed practical radio communication based on Hertz's work.