The Principle of Superposition
The Principle of Superposition
- Two waves can occupy the same place at the same time. They pass through one another rather than colliding like objects.
- While they overlap, each point responds to both waves. Its new displacement is found by adding their displacements with signs.
Add at one point first
- Upward displacement is positive and downward displacement is negative. For example, .
- Repeat this addition at every position to draw the whole resultant wave.
- The original waves continue after the overlap. Superposition does not make either wave disappear permanently.
Superposition is local and signed: add the displacements at the same position and the same instant.
The exam statement
Definition
2 marksWhat is meant by the principle of superposition?
Model answer: When two or more waves overlap, the resultant displacement at a point is the algebraic sum of the individual displacements at that point.
Common mistake
Add displacement, not amplitude. Amplitude is the largest possible displacement of a wave; the displacement at the chosen instant may be smaller or negative.
Your turn9702/21/M/J/25 Q4(a)
State the principle of superposition of waves. [2] (9702/21/M/J/25 Q4(a))
Show worked answer
When two or more waves overlap, the resultant displacement at a point is the sum of the individual displacements at that point.