August Herman Pfund (28.12.1879-4.01.1949) — American physicist. Born in Madison (Wisconsin). In 1910—47 he worked at Johns Hopkins University in Baltimore (from 1927 as a professor and from 1938 as dean of the physics faculty).
His work concerned optics and spectroscopy, in particular the study of infrared radiation. He improved (1912) the thermocouple and studied (1916) the photoconductivity of copper oxide. He constructed a source of the iron spectrum (the Pfund arc) and in 1927 a diffraction spectrograph, improved in 1931 by Hardy (the Pfund–Hardy spectrograph). He was the first to propose (1930) the use of powder films as infrared filters, and in 1933 created a filter from quartz powder. He showed that selenium can serve as a good polariser of infrared radiation. He discovered a spectral series (the Pfund series).
In 1943 he was president of the Optical Society of America.