共查询到20条相似文献,搜索用时 46 毫秒
1.
J. Satyanarayana Murty B. Ramachandra Rao 《Zeitschrift für Physik A Hadrons and Nuclei》1959,157(2):189-197
A method of generating, simultaneously, two sound waves of frequencies in the ratio 1∶n, whose phase difference can be continuously varied, is described. The diffraction of light by such waves is studied, using frequencies in the ratio 1∶2 and 1∶3. Quantitative measurement of the intensities of the various orders is carried out, at phase angles of 0,π/2 and π in case of 1∶2 waves and at phase angles of 0 andρ in case of 1∶3 waves. The measured intensities compared very well with values calculated on the basis of the simple theory worked out by Murty. Photographs, showing the general features of diffraction by superposed waves, have also been reproduced. 相似文献
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The aim of the present paper is to study the revolving superposed standing waves in a spinning Timoshenko beam based on the results obtained by the first author with others in two recently published papers. The concept of superposed standing wave as normal mode and the knowledge about the helical feature of propagating wave will be used to depict a physical picture about the vibration of the spinning beam, from describing the basic constituent waves to showing the orthogonality property of the revolving normal modes. The wave-mechanics approach will be invoked throughout the study with an algebraic procedure used to reveal the two eigenvalues of the gyroscopic-coupling phase factor. A table for tabulating the phases of the centroidal positions of the beam in time and space due to the passing of a wave is invented, through which one could show the helical structure of the wave without ambiguity. From the present result, two types of revolving standing waves are identified, each manifesting as a gyroscopic precession in association with a frequency-splitting phenomenon, in either the clockwise or the anticlockwise direction. It is shown that the revolving waves should be represented by wavefunctions in a form of four-component column matrix vectors. 相似文献
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The theory of boundary diffraction wave is generalized to the case of multiple Fresnel-Kirchhoff diffraction on several sequentially
situated holes (screens). The generalized boundary wave is the sum of boundary diffraction waves with different multiplicities
described by integrals whose maximal multiplicity is equal to the number of obstacles. It is shown that the proposed generalized
boundary wave method provides a multiple time gain in calculations, as compared to the aperture integration method. Results
of numerical calculations agree with experimental dependences. 相似文献
4.
Interaction of the fundamental shear horizontal mode with through-thickness cracks in an isotropic plate is studied in the context of low frequency array imaging for ultrasonic guided wave nondestructive evaluation with improved resolution. Circular wave fronts are used and the symmetric case where a line from the wave source bisects the crack face normally is considered. Finite element simulations are employed to obtain trends subject to analytical and experimental validation. The influence of the crack length and of the location of source and measurement positions on the specular reflection from the crack face is first examined. These studies show that low frequency short range scattering is strongly affected by diffraction phenomena, leading to focusing of energy by the crack in the backscatter direction. Study of the diffraction from the crack edges reveals contributions due to a direct diffraction at the edges and multiple reverberations across the crack length. A simple diffraction model is shown to adequately represent cracks up to moderate lengths, providing an easy means of estimating the far field of the waves. The presence of multiple diffraction components is quantitatively established and surface waves on the crack face are identified as equivalent to low frequency symmetric modes of rectangular ridge waveguides. 相似文献
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L. M. Serebryakova 《Optics and Spectroscopy》2000,89(5):783-791
Assuming arbitrary correlation between the recorded and read-out fields and taking into account all the effects of inter-and cross-modulation diffraction structures, expressions are derived that describe in the most general form the spatial modulation of the original object and reference waves in the response of thin linear and quadratic off-axis holograms with superimposed recording. Associative data reconstruction is discussed. 相似文献
8.
V. V. Orlov 《Optics and Spectroscopy》2002,92(6):948-955
Crosstalks of three-dimensional superimposed holograms, caused by multiple wave diffraction at crossmodulation and intermodulation hologram gratings, were studied. It was shown that the intensity of these interferences depends on the method of data coding in physical parameters of hologram object waves during holographic recording. A coding method efficiently lowering the interference intensity was considered. 相似文献
9.
理论上分析了超声光栅衍射和液体表面波光栅衍射,得到了表面波光栅衍射图样与表面波参数的解析关系.实验上得到清晰的衍射图样,利用表面波光栅衍射法测量了液体表面波波速,实验结果与理论值误差不超过1%. 相似文献
10.
We discuss electron diffraction from two counterpropagating light waves with two different frequencies. We show that, even though these waves do not form a standing wave, electron diffraction similar to the conventional Kapitza-Dirac effect, i.e., scattering on a standing wave, is still possible. The nonlinear response of the electron to the laser fields creates a stationary diffraction grating from which the same electron scatters. 相似文献
11.
激光衍射法测量表面张力和毛细波波速与温度的关系 总被引:1,自引:1,他引:0
利用激光衍射对液体表面张力和毛细波波速与温度的关系进行了研究.当激光斜入射到毛细波上,观察到稳定的、清晰的衍射图样,运用光栅衍射理论对该实验现象进行了分析,测量了不同温度下蒸馏水的表面张力和毛细波波速,用最小二乘法对实验数据进行拟合,给出了表面张力和毛细波波速与温度的解析关系,发现表面张力和毛细波波速随着温度的增加而减小,并和温度呈近似线性关系.根据其机理,建立了激光衍射法实时的和非接触的测量不同温度下液体表面张力和毛细波波速的方法. 相似文献
12.
Kline JL Montgomery DS Bezzerides B Cobble JA DuBois DF Johnson RP Rose HA Yin L Vu HX 《Physical review letters》2005,94(17):175003
Thomson scattering is used to measure Langmuir waves (LW) driven by stimulated Raman scattering (SRS) in a diffraction limited laser focal spot. For SRS at wave numbers klambda(D) less similar 0.29, where k is the LW number and lambda(D) is the Debye length, multiple waves are detected and are attributed to the Langmuir decay instability (LDI) driven by the primary LW. At klambda(D) greater similar 0.29, a single wave, frequency-broadened spectrum is observed. The transition from the fluid to the kinetic regime is qualitatively consistent with particle-in-cell simulations and crossing of the LDI amplitude threshold above that for LW self-focusing. 相似文献
13.
The integral expression for divergent spherical waves diffracted at an annular aperture is derived based on the theory of the boundary diffraction wave. The expressions for divergent spherical waves diffracted at a circular aperture and a disk, and the axial field are treated as the special cases of our general one. Numerical calculation results for axial and transversal intensity distributions are given to compare our results with the Kirchhoff diffraction integral, first and second Rayleigh diffraction integrals. As expected, our results are in agreement with those in the use of the Kirchhoff diffraction integral, but the computer time is reduced greatly by using the boundary diffraction wave theory. The four diffraction formulae are shown to be consistent for axial and transversal intensity distributions, if the source and observation points are positioned equally from the aperture, or the observation point is located enough far from the aperture. Otherwise, the mean value of the first and second Rayleigh diffraction integrals is equal to the result of the boundary diffraction wave theory. 相似文献
14.
A. Gedeon 《Applied physics. B, Lasers and optics》1973,2(1):15-22
Efficient focussing of surface acoustic waves has been achieved using a properly shaped gold film deposit on the −22.3° rotated
Y-cut surface of quartz. The acoustic wave field was studied with laser probing techniques. A more than threefold increase
in intensity and a tenfold decrease in beam width was observed at the focal point. The focussing action was obtained with
the elastic wave equivalent of the Fresnel phase-reversal zone plate of optics. The multiple foci of this device allowed a
simultaneous generation of acoustic waves in nearly all directions on the surface. Consequently, the surface wave velocity
anisotropy could be determined completely. The experimental results are in very good agreement with the calculated velocity
anisotropy. Electromagnetic diffraction theory is adopted to the two dimensional anisotropic system to analyse the performance
of the focussing device. 相似文献
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Yusuf Ziya Umul 《Optics Communications》2012,285(6):929-933
The line integral of the boundary diffraction wave theory is extended for the diffraction process of waves by the impedance surfaces with edge discontinuities. With this aim, the exact diffraction field expression of Maliuzhinets is transformed into a line integral. The method is applied to the scattering problems of waves by a spherical reflector with edge discontinuity and the diffracted fields are evaluated asymptotically. The resultant expressions of the waves are examined numerically. 相似文献
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Polarization anomalies of the Brewster type are considered for processes such as wave reflection, wave scattering, wave diffraction by surface grating and surface plasmon waves. Generalized conditions for Brewster anomalies in wave diffraction are written in analytical form. The application of the Brewster phenomenon for integrated optical polarizers is investigated numerically. 相似文献
19.
Yu.P. Bliokh 《Optics Communications》2006,259(2):436-444
It is shown that a smooth metal film (or a plasma layer) can be made transparent for an electromagnetic wave when two identical subwavelength diffraction gratings are placed on both sides of the film. The electromagnetic wave transmission through the metal film is caused by excitation of evanescent surface waves (plasmons) and their transformation into propagating waves at the gratings. A model which is developed analytically shows that the problem of the wave transmission is physically equivalent to the problem of excitation of two coupled resonators of evanescent waves which are formed at the two film surfaces. 相似文献
20.
Yusuf Ziya Umul 《Optics & Laser Technology》2012,44(5):1312-1317
The line integral of the boundary diffraction wave theory is derived for the diffraction process of waves by a junction between two surfaces with different face impedances. The exact solution of Maliuzhinets is used with this aim. The resultant integral is applied to the diffraction of waves by a circular junction between two impedance surfaces. The results are examined numerically. 相似文献