What is the principle of superposition?

When waves overlap the resultant displacement is the sum of their individual displacements.

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When does constructive superposition occur?

When overlapping waves are in phase which means the peaks and troughs are aligned. 


Constructive superposition results in a wave with a larger amplitude.

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When does destructive superposition occur?

When overlapping waves are out of phase which means the peak of one wave is aligned with the trough of another. 


This results in a wave with a smaller amplitude or complete cancellation.

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What is the phase difference between two waves which completely destructively superpose?

180°  OR  π radians

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What is the phase difference between two waves which interfere constructively?

0°  OR  2π radians

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Explain what is meant when two waves are coherent.

Two waves are coherent if they have:

  1. same wavelength
  2. same frequency
  3. fixed phase difference

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What is the path difference (in terms of λ\lambda) of two waves that constructively superpose?

nλ


n = any integer number

λ\lambda = wavelength (m) 

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What is the path difference (in terms of λ\lambda ) of two waves that destructively superpose?

(n +21​)λ


n = any integer value

λ\lambda= wavelength (m) 

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