Lummer, Otto Richard (1860–1925)

German physicist who specialized in optics and thermal radiation. His investigations led directly to the radiation formula of Max Planck, which marked the beginning of quantum theory.

Lummer was born in Jena, Saxony, and attended a number of different German universities. He became an assistant to Hermann Helmholtz at Berlin 1884 and moved with him to the newly established Physikalische Technische Reichsanstalt in Berlin 1887. In 1894 Lummer was made professor there. From 1904 he was professor at Breslau (now Wrocław, Poland).

In collaboration with Eugen Brodhun, he designed a photometer (the Lummer–Brodhun cube) and worked towards the establishment of an international standard of luminosity. Lummer and Wilhelm Wien made the first practical black-body radiator by making a small aperture in a hollow sphere. When heated to a particular temperature, it behaved like an ideal black body. Studying emission from black bodies, Lummer later confirmed Wien's displacement law but found an anomaly in Wien's radiation law.

Lummer designed a mercury vapour lamp for use when monochromatic light is required, for instance in fluorescence microscopy, and in 1902 designed a high-resolution spectroscope.