Sound Waves In Water Research Articles

A Supersonic Cell Fluorometer

A method is described for the measurement of the rise and decay of luminescence in phosphors excited by cathode-ray beams. It is particularly suited to the investigation of phosphors classed as fast, i.e., those in which major changes in intensity occur in a few microseconds. The method is based on the use of a supersonic cell arranged to produce the Debye-Sears diffraction effect. High speed shutter action is obtained by modulating the supersonic wave train to produce short steep-sided pulses. Light intensities sufficient for direct measurement in terms of photoelectric cell response are obtained by synchronizing the periodic excitation of the phosphor with the diffracting wave pulses in the liquid. Time intervals in the decay process are measured in terms of distances traversed by the sound waves in water. Several methods of using the device are described, and some results obtained by these methods are shown.

The Origin of the Absorption of Ultrasonic Waves in Liquids

It seems now experimentally certain that the absorption of sound waves in water, benzene, carbon tetrachloride and methyl alcohol is strictly proportional to the square of the frequency up to 50 megacycles, but considerably larger than can be explained by viscosity and heat conduction. It is shown here that an explanation of this increased absorption by slowness of energy exchange between internal and external degrees of freedom is not in disagreement with the facts for the three last named liquids, while the absorption in water must have a different origin.