Wize University Physics Textbook (Master) > Waves: Mechanical

Principals of Superposition: Waves

Interference and Superposition

Image illustrating Interference and Superposition

The overlapping of waves is called interference. They combine as they pass through each other while traveling in the medium.

Principle of Superposition: When two waves overlap, the actual displacement of any particle in the medium is the algebraic sum of their displacement due to each wave if only that wave were present:

y\left(x,t\right)=y_1\left(x,t\right)+y_2\left(x,t\right)

Example: Superposition

Two waves approach each other, both moving at speed of $1$ m/s. What happens at $t = 4$ s?

After 4 seconds of moving towards each other, the waves will overlap like this:

For each time value, add the amplitudes of the two waves. The superposition will look like this:

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Practice: Superposition

You have a snapshot of two waves on a string as shown below, at $t = 0$ s . They are moving towards each other.

The wave on the left is moving at $+ 2.0$ m/s. The wave on the right is moving at $-1.0$ m/s. Sketch what happens at $t = 2$ s.

Illustration for practice question: Practice: Superposition

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