Classic Science Paper: Otto Wiener’s experiment (1890) at Skulls in the Stars.

By 1890, then, scientists were interested in seeing whether similar results held for light waves: it seems that a number of scientists remained unconvinced that light truly was just another manifestation of electromagnetic waves! One big obstacle stood in the path of such studies: the smallness of the wavelength of light. Hertz’s radio waves had a wavelength of meters, but visible light has a wavelength on the order of 500 nanometers, or 500 billionths of a meter! Such distances cannot be directly observed with the naked eye, so experimental ingenuity was required – and Otto Wiener provided it.

(My own summary of some “classic” physics is progressing)