![]() ![]() So, it makes sense that lower-frequency sounds typically have a wide dispersion and sounds with small wavelenths have a narrow dispersion. ![]() Conversely, if the ratio of W/D is small, then x is small and the waves are said to have a narrow dispersion and the sound waves go through the opening without spreading out very much. In this case, the waves are said to have a wide dispersion and the sound waves are spread out wider through the opening. If the ratio of W/D is large, then x is large. So, looking at these two equations you can tell that the extent of the diffraction depends on the ratio of the wavelength to the size and shape of the opening. Angle x, W for wavelength, and D for width are all still the same. For a circular opening, the equation is slightly different. Gives x in terms of the wavelength and the width of the doorway. If we let angle x be the location of the first minimum intensity point on either side of the center, W be the wavelength, and D be the width of the doorway, the equation Waves diffract differently depending on the object they are bending around. Each maxima gets progressively softer further away from the center. As you move further away from the center, the intensity decreases until it is at zero, then increases to a maximum, falls to zero, rises to a maximum.and so on. Directly in front of the center of the doorway the intensity is a maximum. Ripple tank demonstrations are commonly done in a Physics class in order to discuss the principles underlying the reflection, refraction, and diffraction of waves. The sound outside of the room has varying intensity depending on where you stand. The final result is the diffraction of the sound wave around the doorway. This results in each molecule producing a sound wave and emitting it outward in a spherical fashion. This means that each air molecule is a source of a sound wave itself. ![]() Instead, the air in the doorway is set into longitudinal vibration by the sound waves from the stereo. The great thing about this way of thinking about diraction is that, since the wave equation is linear, you can use this trick for any number of holes. Without diffraction, the sound from the stereo could only be heard directly in front of the door. All waves exhibit diffraction, not just sound waves. This bending of a wave is called diffraction. For example, if a stereo is playing in a room with the door open, the sound produced by the stereo will bend around the walls surrounding the opening. An obstacle is no match for a sound wave the wave simply bends around it. ![]()
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