Overall Intensity of Destructively Interfering Waves

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Discussion Overview

The discussion revolves around the intensity of sound waves from two sources that are emitting in phase and undergoing destructive interference. Participants explore the implications of this interference on the intensity at specific points, considering both definitions of intensity and the geometry of wave propagation.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the intensity at points of destructive interference is zero or the sum of the intensities of the individual sources.
  • Another participant asserts that the intensity is zero at points of destructive interference.
  • A third participant supports the claim of zero intensity by referencing the definition of intensity as proportional to the square of the amplitude, stating that zero amplitude results in zero intensity.
  • Additionally, a participant notes that destructive interference can occur along a line between the two sources, while along the line connecting the sources, a standing wave is formed.

Areas of Agreement / Disagreement

There is disagreement regarding the intensity at points of destructive interference, with some participants asserting it is zero while others question this conclusion. The discussion remains unresolved as participants explore different aspects of the problem.

Contextual Notes

The discussion does not clarify the assumptions regarding the conditions under which the waves are considered to interfere destructively, nor does it address potential variations in amplitude or distance from the sources.

JSGandora
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If you have two sound sources emitting the same frequency and in phase with each other such that the emitted waves destructively interfere along the line containing the two sources, is the intensity at the points 0 or the sum of the intensity of each source independently?
 
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zero
 
You can check this from the definition of "intensity" - it is proportional to the square of the amplitude.
If the amplitude is zero then the intensity must be zero.
 
Also note that the waves might interfere destructively along a line that passes between the two sound sources, not along a line that connects the sources. Along that second line you'll form a standing wave.
 

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