Balmer, Johann Jakob (1825–1898)

Swiss physicist and mathematician who developed a formula in 1884 that gave the wavelengths of the light emitted by the hydrogen atom (the hydrogen spectrum). This simple formula played a central role in the development of spectral and atomic theory.

Balmer was born near Basel, where he taught school for 40 years. Although a mathematician and not trained in physics, he became interested in spectroscopy. In 1885 he published an equation that described the four visible spectral lines of hydrogen (all that were then known) and also predicted the existence of a fifth line at the limit of the visible spectrum, which was soon detected and measured. He further predicted the existence of other hydrogen spectral lines beyond the visible spectrum. The five lines in the visible part of the hydrogen spectrum are now known as the Balmer series.