Lord Rayleigh proposed the liquid surface-tension method used in Bohr's 1905 prize work.
Rayleigh's 1879 theory connected the surface vibrations of a liquid jet with the liquid's surface tension. The Danish Academy's competition asked entrants to investigate this method quantitatively. Bohr, then a young University of Copenhagen student, chose water as his experimental subject and studied the waves and oscillations formed in a vibrating jet.
Bohr's work was not merely a routine application. He improved Rayleigh's treatment by considering effects such as the liquid's viscosity and the surrounding air, and he extended the analysis beyond very small vibration amplitudes. Because Copenhagen University did not have a physics laboratory, he performed much of the work in his father Christian Bohr's physiology laboratory, often at night to reduce disturbances.
The paper was submitted in 1906, and the Royal Danish Academy notified Bohr in February 1907 that he had won its gold medal. A revised English version became Bohr's first published paper in 1909. This early experimental success preceded his later theoretical work on atomic structure.