Gustav Kirchhoff, German physicist, mid-19th century.
© Science Museum / Science & Society Picture Library
Etching after a photograph of Gustav Robert Kirchhoff (1824-1887), who distinguished himself in many fields, notably in the study of electricity, heat, optics and especially for his contributions to spectrum-analysis. He formulated Kirchhoff's law of radiation, the key to the whole thermodynamics of radiation, and his electromagnetic theory of diffraction is today still the most commonly used in optics. Published by the International Telecommunication Union. Dimensions: 230 mm x 190 mm.