Question
Write and explain the super position principle (of waves).

Answer

• Super Position Principle :
"At a particular point in the medium, the resultant displacement produced by a number of waves is the vector sum of the displacements produced by each of the waves."
Image

As shown in fig. (a), two waves are moving towards each other on a string.
Suppose, the maximum displacement of the particle under the effect of first wave is 0.5 cm and in the second wave, the maximum displacement is 0.3 cm .
Here, both the waves are moving towards each other.
As the two waves are approaching each other, at any instant both the waves will overlap in some region of the string. Then they move with their original shape and in their original direction.
The net maximum displacement of the particle of string in overlapped region would be 0.5 cm $+0.3 cm=0.8 cm$
Suppose, two persons snap the end of the string such that wave pulse generates at both the ends of the string as shown in fig. (b). In the first wave pulse the maximum displacement of the particle is 0.5 cm in upward and in the other wave pulse the maximum displacement of the particle is 0.5 cm in the downward direction.
When the wave pulses approach each other, at some instant, they overlay on the string and displacement of all the particles will be 0.5 cm $+(-0.5 cm)=0$.
Here, the velocities of the particles will not be zero.
In this situation, string becomes stright everywhere, then both the wave pulses will emerge and move in their original direction.



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