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通过采用将入射光掠入射到频率为几百赫兹的衰减低频液体表面波上,观察到了清晰的间距分布具有明显非对称性的衍射条纹。当入射光掠入射到低频液体表面上时,衍射图样非对称分布具有普遍性。理论上得到了考虑表面波衰减影响后观察屏处衍射光强分布的解析表达式。理论结果表明:衍射图样的这种非对称分布与衍射级次、入射光波波长、液体表面波波长及表面波衰减系数有关;正负级次衍射亮条纹距离中央零级亮条纹的间距体现表面波衰减信息;正衍射级次之间以及负衍射级次之间的条纹间距体现表面波波长信息。利用所提出的方法实现了对几百赫兹液体表面波的衰减系数的实时便捷测量。
By using grazing incidence of incident light onto a damped low frequency liquid surface wave at a frequency of a few hundred hertz, diffraction stripes with distinctly asymmetric spacing distributions were observed. When the incident light grazing incidence on the surface of low-frequency liquid, the asymmetric distribution of diffraction patterns is universal. In theory, the analytic expression of diffracted light intensity distribution at the observation screen after the influence of surface wave attenuation is obtained. The theoretical results show that the asymmetric distribution of diffraction pattern is related to diffraction order, incident light wavelength, liquid surface wave wavelength and surface wave attenuation coefficient. The spacing between the bright and blue stripes of positive and negative orders from the central zero- Attenuation information; the stripe spacing between the positive diffraction orders and the negative diffraction orders embodies surface wave wavelength information. Using the proposed method, a real-time and convenient measurement of the attenuation coefficient of several hundred Hertz liquid surface waves is achieved.