Undulatory theory of light

ISIS Joseph Fraunhofer (1787-1826) exhibited his newest spectroscope before Counselor Utzschneider and Mr. Reichenbach, his partners in the glassworks and optical establishment at Benediktbenem. He discussed with them his latest researches on the diffraction of light which had led him to the discovery of grating spectra, the exact measurement of wave lengths, and a brilliant confirmation of tile undulatory theory of light. 

The controversy was settled in favour of the undulatory theory because the latter could immediately give a reasonable explanation of interference and diffraction phenomena. Again the observation (Foucault) that the velocity of propagation of light in a medium is less than in a vacuum was in contradiction to the emission theory. 

Today it is difiicult to imagine the complacency of the physicist of 1890. Classical physics was a house in order mechanics, thermodynamics, kinetic theory, optics, and electromagnetic theory were the main foundations—an imposing display. By choosing tools from the appropriate discipline any problem could be solved. Of course, there were one or two problems that were giving some trouble, but everyone was confident that these would soon yield under the usual attack. There were two parts in this house of physics the corpuscular and the undulatory, or the domain of the particle and the domain of the wave. Matter was corpuscular, light was undulatory, and that was that. The joint between matter and light did not seem very smooth. 

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