Superposition of Waves (DP IB Physics): Revision Note

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

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

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

• Interference is the effect of this overlap

  • This is explained in the next Interference of Waves

• 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

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