Elizabeth Hertz, wife of Heinrich Hertz, and their eldest daughter Johanne, 1889.
© Science Museum / Science & Society Picture Library
Photograph. 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.