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Wave Behavior

Unit 9: Waves and Sound

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Wave Boundary

  • The behavior of a wave (or pulse) upon reaching the end of a medium is referred to as boundary behavior
  • When one medium ends, another medium begins
  • The interference of two media is referred to as a boundary
  • The behavior of a wave at that boundary is described as its boundary behavior

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  • Reflection, refraction, and diffraction are all types of boundary behavior

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Reflection

  • When a wave bounces off a barrier
    • Ex: An echo is reflected sound waves

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Reflection

  • Reflections off a flat barrier (like a bathroom mirror) follow the law of reflection
    • Angle of incidence = angle of reflection

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Refraction

  • The change in the speed of a wave as it moves from one medium into another
  • Refraction is always accompanied by a change in wavelength and speed
    • Ex: Pencil in glass of water looks like it is bending
      • Light waves travel faster in air than in water
      • Larger speed change means a bigger difference

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Diffraction

  • The bending of waves around a barrier or opening
    • The amount of diffraction increases with increasing wavelength

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Diffraction

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Interference

  • When two waves meet while traveling along the same medium there is interference
    • The waves will pass through each other then continue to travel on in their original form

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Constructive Interference

  • Constructive interference occurs when both waves have displacement in the same direction
  • The result will be a larger displacement in the same direction as the individual displacements
  • The amplitude will be temporarily larger as the waves pass through each other

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Destructive Interference

  • Destructive interference occurs when two waves in different directions meet
  • A wave with a smaller amplitude will result in the direction of the larger wave

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Principle of Superposition

  • When two waves interfere, the resulting displacement of the medium at any location is the sum of the displacements of the individual waves at the same location

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These unusually shaped wave pulses are heading towards each other in a medium whose wave speed is one square per second. Draw the resulting shape of the medium one, two, and three seconds later.

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