Etching by F Tonnelat of Hertz (1857-1894) who discovered 'Hertzian waves', (electromagnetic waves) and found that they behave like light waves except for their wavelength. He was reputedly the first man to broadcast and receive radio waves and the unit of frequency of radio waves is named after him. Published by the International Telecommunication Union. Dimensions: 230 mm x 190 mm.
© Science Museum / Science & Society Picture Library