Walther Ritz (22.02.1878-7.07.1909) was a Swiss theoretical physicist and mathematician. He was born in Sion. He graduated from the University of Zurich (1900). He worked in Göttingen, Bonn, Paris, Zurich and Tübingen.
His work in physics was on spectroscopy, the theory of thermal radiation and electrodynamics. In 1908 he discovered the law according to which the wave number of any spectral line is equal to the difference of two terms from the set of terms characteristic of a given element.
The formula describing any spectral line of an element was given in 1890 by J. Rydberg. Hence the name “Rydberg — Ritz principle”, or “Rydberg — Ritz combination principle”. In mathematics he is known for the “Ritz method”, a method of solving variational problems (1908).