Explain the mechanism of formation of ta longitudinal wave when a source vibrates in air?
Answers
When a source of sound vibrates, it creates a periodic disturbance in the medium near it (i.e., the condition of medium changes). The disturbance then travels in the medium in form of waves. This can be understood by the following example.
Example: Take a vertical metal strip with its lower end fixed. Push its upper end to one side and then release it. As it vibrates, i.e. moves alternately to the right and left, the sound is produced. The figure shows the steady (or mean position) of the metal strip and normal condition of air layers near the strip.
As the strip moves to the right from a to b in Figure it pushes the particles of air layer in front of it. So the particles of air in this layer come closer to each other i. e., air in that layer gets compressed (or compression is formed at C). The particles of this layer while moving towards right, pushes and compresses the layer next to it, which then compresses the next layer and so on. Thus the disturbance moves forward in form of compression. The particles of the medium do not move with the compression. As the metal strip starts returning from b to a in Figure after pushing the particles near the strip, the compression C moves forward and the particles of air near the strip return back to their normal positions due to the elasticity of medium
For a sound wave traveling through air, the vibrations of the particles are best described as longitudinal. ... As the vibrating string moves in the reverse direction (leftward), it lowers the pressure of the air immediately to its right, thus causing air molecules to move back leftward.
#lordcarbin
#devilwillrise