Superposition of Waves (DP IB Physics) : Revision Note

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Superposition of Waves

  • When two or more waves arrive at the same point and overlap, their amplitudes combine 

    • This is called superposition

  • The principle of superposition states that:

    When two or more waves overlap at a point, the displacement at that point is equal to the sum of the displacements of the individual waves

  • The superposition of surface water waves shows the effect of this overlap

    • There are areas of zero displacement, where the water is flat

    • There are areas of increased displacement, where the water waves are higher

superposition-water-waves-example

The dogs make waves in the water which superimpose to give areas of both zero and increased displacement.

  • It is possible to analyse superposition clearly when the waves are drawn on a vertical displacement (amplitude)-displacement graph

superposition-graph

Waves can superimpose so their amplitudes are added together often creating a larger resultant amplitude

  • Interference is the effect of this overlap

  • Individual wave displacements may be positive or negative and are combined in the same way as other vector quantities

  • It is possible to analyse superposition clearly when the waves are drawn on a displacement-time graph 

  • Superposition can also be demonstrated with two pulses

    • When the pulses meet, the resultant displacement is also the algebraic sum of the displacement of the individual pulses

    • After the pulses have interacted, they then carry on as normal

4-3-3-superposition-of-pulses_sl-physics-rn

When two pulses overlap their displacements combine to form a resultant displacement

Worked Example

Two overlapping waves of the same type travel in the same direction. The variation with x and y displacement of the wave is shown in the figure below.

Use the principle of superposition to sketch the resultant wave.

Answer:

Worked example - superposition (2), downloadable AS & A Level Physics revision notes
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Ashika

Author: Ashika

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Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.

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