Non-uniform Distribution Of Interference Fringe Intensity On The Liquid Surface And The Attenuation Effect Of Surface Acoustic Waves

Surface acoustic waves (SAW) is a kind of elastic wave, the propagating energy of which concentrates on the medium (solid or liquid) surface. SAW travels along the medium surface, which carries a large number of surface information. Therefore SAW research has already brought to more and more attentions. Through measuring the property of SAW, which propagates along the surface, one can obtain medium characteristic of surface. For example, by detecting metal SAW, one may examine the crack, the flaw of metal surface and so on; by measuring the SAW of liquid surface, one can gain the liquid surface parameter, such as surface tension, viscous coefficient and so on.This thesis mainly includes four parts.The first part introduces water wave and SAW, involving the wave classification, the wave research as well as SAW detection method. Based on different restoring force properties, the ripples are classified, and a detailed instruction to the forming reasons and characteristics of various waves are given. About the SAW, its research history is reviewed and its optics detection method is introduced. According to the difference of the medium, along which the surface sound wave propagates, the detection method is classified, and the general principle, progress, and its application are introduced.The second part is about the non-uniform distribution of interference fringe intensity on the liquid surface. In the interference experiment on the liquid surface, it is found that the intensity of the center fringe is the smallest and the intensity increases gradually towards the two sides. This is different from our former experience. In the existing optical theory, the maximum value of the interference fringe formed by the plane wave, is equal. Moreover, generally in an experiment, due to the incident light is not uniform, it is observed that the center intensity is the biggest and it decreases towards the two sides. An analytic intensity distribution expression is derived theoretically, which provides a reasonable explanation to this phenomenon.In the third part of this thesis, some elementary knowledge in hydrodynamics was introduced in detail. Some basic concepts are introduced, such as viscosity, the...