Herman Haga (Oldeboorn, 24 January 1852 – Zeist, 11 September 1936) was a Dutch physicist.

Career

Haga studied physics from 1871 to 1876 at the University of Leiden.^[1] He received his PhD with thesis Over de absorptie van stralende warmte door waterdamp (On the absorption of radiant heat by water vapor)^[2] under the direction of Pieter L. Rijke. From 1886 to 1921 Haga was professor of physics at the University of Groningen, where he designed and oversaw the building of a new physics laboratory, opened in 1892. From 1900 Haga was also the rector of the University of Groningen. He performed experiments on the voltage of the Weston cell; these experiments lead to the modern definition of the volt. With Cornelis Wind, Haga passed X-rays through a 15-micrometer slit as a source with a V-shaped narrowing slit as a target. The target slit was 27 micrometers at the opening and nearly 0 micrometers at the output. Haga and Wind interpreted a diffuse broadening of the X-rays emitted at the narrower end of the slit as a diffraction pattern.^[3][4]

Haga was one of the founders of the Nederlandse Natuurkundige Vereniging (Dutch Physics Association). In addition to Cornelis Harm Wind (1867–1911),^[5] Haga's doctoral students include the crystallographer Pieter Terpstra (1886–1973)^[6] and Ekko Oosterhuis (1886–1966), who was the second scientist to join the Philips Natuurkundig Laboratorium.^[7]

In 1896 Haga became a member of the Royal Netherlands Academy of Arts and Sciences.^[8]