State the principle of superposition of waves.

Explanation

Principle of superposition of waves: The displacement of a particle at a given point in space and time due to the simultaneou influence of two or more waves is the vector sum of the displacements due to each wave acting independently.
Explanation:
Consider two sound waves of the same frequency arrivie simultaneousiy at a point.
(1) If the are in phase, the compression due to one wave coincides with the compreasion due to the other and the rarefaction due to one wave coincides with the rarefaction due to the other. Therefore, the resultant amplitude and hence the resultant intensity at that point becomes minimum. This phenomenon is called constructive interference [fig. (a)]
(2) If they are opposite in phase, the compression due to one wave coincides with the rarefaction due to the other and vice versa. Therefore, the resultant amplitude and hence the resultant intensity at that point becomes minimum. This phenomenon is called destructive interference. If the two waves have the same amplitude, the resultant amplitude and hence the resultant intensity at that point is zero

(3) If the phase difference between the two interfering waves is different from `0 and 180^(@)`, the resultant amplitude lies between `A_ 1 + A_2 and |A_1-A_2|` and hence the resultant intensity at that point is neither maximum, nor zero.