Many students think that two wave pulses travelling in opposite directions will permanently superimpose as opposed to traveling through each other.

Light, Sound and Waves


Resources to Address This

  • Sources in step (14-16)

    Ref - SPT Ra03TL03

    This is an introduction to a series of activities about interference.  It is possible to demonstrate that the waves continue to travel independently beyond the area of intereference.

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  • Watching one ripple crossing another  (11-16)

    Ref - Practical Physics; Waves; Mechanical waves and superposition; 

    Demonstrate two circular waves crossing in a ripple tank.

    • The fact that two waves continue on their way when they have passed through each other as if there had never been an encounter will come as no surprise to students who have:
      • Closely observed raindrops falling in a puddle, or
      • Thought about the fact that signal-carrying microwaves and radio waves pass through each other constantly, particularly in cities dense with communications.
    View Resource
  • Episode 321: Interference patterns (16-19)

    Ref - TAP; Teaching vibrations and waves; Superposition;

    When two or more waves meet, we may observe interference effects. It is likely that your students will have already met the basic ideas of constructive and destructive interference.  Remember to look beyond the area of interference.

    View Resource


The following studies have documented this misconception:

  • Wittmann, M. C. () The object coordination class applied to wave pulses: Analysing student reasoning in wave physics, International Journal of Science Education, London.

    Review sheet

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