Soon, he found out that he could not live with the approximations and compromises associated with engineering, so he switched to the more mathematically accurate physical sciences.

Ritz wrote a dissertation on spectral lines of atoms and received his doctorate with summa cum laude.

The theme later led to the Ritz combination principle and in 1913 to the atomic model of Ernest Rutherford and Niels Bohr.

In the spring of 1903, he heard lectures by Hendrik Antoon Lorentz in Leiden on electrodynamic problems and his new electron theory.

In June 1903 he was in Bonn at the Heinrich Kayser Institute, where he found in potash a spectral line that he had predicted in his dissertation.

As a student, friend or colleague, Ritz had contacts with many contemporary scholars such as Hilbert, Andreas Heinrich Voigt, Hermann Minkowski, Lorentz, Aimé Cotton, Friedrich Paschen, Henri Poincaré and Albert Einstein.

Ritz pointed out seven problems with Maxwell–Lorentz electromagnetic field equations: Instead, he indicated that light is not propagated (in a medium) but is projected.