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This is still destructive interference since the two interfering pulses have opposite displacements. In this case, the destructive nature of the interference does not lead to complete cancellation.
Principle of superposition
The principle of superposition is sometimes stated as follows:
When two waves interfere, the resulting displacement of the medium at any location is the algebraic sum of the displacements of the individual waves at that same location. |
Assume, that we have this situation:
In the cases above, the summing the individual displacements for locations of complete overlap was made out to be an easy task - as easy as simple arithmetic:
Displacement of Pulse 1 | Displacement of Pulse 2 | = | Resulting Displacement |
+1 | +1 | = | +2 |
-1 | -1 | = | -2 |
+1 | -1 | = | 0 |
+1 | -2 | = | -1 |
Ø Coherence
This is a property holding for two or more waves with logical and consistent ability of sticking together, it is a wave feature marked with an orderly correlation between waves having identical physical quantities."Coherence describes all properties of the correlation between physical quantities of a single wave, or between several waves or wave packets"[1].This physical phenomena can be observed in practical lab experiment carried out to study characteristics of wave properties, the concept of wave coherence can be clearly visible when individual waves exhibit a constructive interference; a state at which the waves sum up and produce a compound sinusoidal wave form with an amplified crest as shown in Pic 1.The wave in blue color is the resultant wave of the two lime waves.
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