Diffraction of Light by Ultra-Sonic Waves

Abstract

F. H. SANDERS¹, in a recent note in these columns, has reported excellent agreement between our theory and his experimental results. His note, however, calls for a statement from us clarifying the theoretical position. As is well known, Debye and Sears in America and Lucas and Biquard in France discovered, in 1932, that a beam of light after passing through a supersonic field breaks up into a fan of diffraction spectra. Following this discovery, Prof. R. Br, of Zurich, carried out extensive investigations regarding the nature of the phenomenon; he obtained numerous beautiful results concerning the manner in which the relative intensities of the various diffraction spectra depend on the wave-length of light, the supersonic intensity and the thickness of the cell. He also discovered that the frequencies of light in the diffracted spectra are modulated by the sound field in a very peculiar manner depending on the order of the spectrum.