![]() Only at the edges there will be a continuation of the plane wave plus an interference from the part of the wave that scattered at the edge, a bit of difraction, which, as the wavelength is small, will be of small extent in the shadow of the obstacle. Earlier work on this problem such as, for example, that by Jones '5 on the diffraction of waves by thick semi- infinite plates, appears to be. An approximate and relatively simple expression for the doubleedge diffraction by a thick threesided barrier is given based on the single wedge diffraction solution and on concepts inherent to the geometrical theory of diffraction which reduces to finite and realistic limits when either source or listener are near the extended plane of. Think of the two limits:ġ) if wavelength is very much larger than obstacle, a piece of wood in the water, the wood is essentially a part of the mass of the water that is undergoing the up and down motion, not distinguishable from water and allows the energy to go through without effect.Ģ)if the wavelength is very small with respect to the obstacle, the part of the wave hitting the obstacle will give up all its energy on the obstacle and be absorbed. diffraction of sound around a three-sided barrier. As we have seen previously, light obeys the equation c f, where c 3.00 × 10 8 m/s is the speed of light in vacuum, f is the frequency of the electromagnetic wave in Hz (or s 1 ), and is its wavelength in m. It all depends on how a plane wave reacts to and obstacle. Diffraction and Interference We know that visible light is the type of electromagnetic wave to which our eyes responds. If the wave length is very large the slit acts as a point source for the dispersion of energy. As with the diffraction in the substrate, the geometry of the system dictates that the particles are within the near-field of the sound field, in this region. If the wave length were made very small then it would pass through with only a small dispersion at the edge. It is analogous to what happens to water waves going through a slit, demonstrated here at about 2'30", one sees that the shorter the wavelength the more narrow the diffraction pattern. ![]() The water wave will diffract at the edges, but with respect to the size of the boat it will be like a small shadow. INTRODUCTION The possibility of using barriers as a means of re- ducing noise near highways 1 and airport runways has revived interest in the classical problem. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |