Heinrich Hertz, German physicist, 1894.
© Science Museum / Science & Society Picture Library
Engraving from 'The Electrician'. Hertz (1857-1894) discovered 'Hertzian waves' (electromagnetic waves) and discovered that they behaved like light waves except for their wavelength. He was reputedly the first person to transmit and receive radio waves and the unit of frequency of radio waves is named after him.