17.3 Behaviors of Waves

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17.3 Behaviors of Waves

• Reflection
• Refraction
• Diffraction
• Constructive Interference
• Destructive Interference
• Standing Waves

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Reflection

• When a wave bounces off a surface that it cannot
  pass through
• Ex. ball cant pass through a wall, so it
  bounces off
• Reflection does not change the speed or frequency
  of a wave, but the wave can be flipped upside
  down
• Fixed boundary ? reflected wave upside down

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Refraction

• The bending of a wave as it enters a new medium
  at an angle
• Occurs when a wave enters a medium at an angle
• One side of the wave moves more slowly than the
  other side
• Refraction applet
• In this case, v different refractive value for
  a different medium

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Diffraction
5
Diffraction PhET diffraction applet

• The bending of a wave as it moves around an
  obstacle or passes through a narrow opening
• A wave diffracts more if its wavelength is large
  compared to the size of an opening or obstacle
• If wavelength lt opening/obstacle, then very
  little bending
• If wavelength gt opening/obstacle, then larger
  bending

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Interference

• When 2 or more waves overlap and combine together
• 2 types of interference
• Constructive (leads to increased amplitude)
• Destructive (leads to decreased amplitude)

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Constructive interference

• When 2 or more waves combine to produce a wave
  with a larger displacement (amplitude)

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Destructive Interference

• When 2 or more waves combine to produce a wave
  with a smaller displacement (amplitude)

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Standing Waves

• A wave that appears to stay in one place it
  does not seem to move through the medium
• Examples plucked guitar string or elastic cord
• Node a stationary point on a standing wave
• Complete destructive interference between
  incoming and reflected waves
• Antinode a point where a crest or trough occurs
  midway between nodes
• Forms only if a wavelength or a multiple of half
  a wavelength fits exactly into the length of a
  vibrating cord.

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Standing Waves

• Links to Standing Waves Applets
• Standing wave created by reflecting off of 1
  barrier
• http//faraday.physics.utoronto.ca/IYearLab/Intros
  /StandingWaves/Flash/reflect.html
• Standing wave created by reflecting off 2
  barriers
• http//faraday.physics.utoronto.ca/IYearLab/Intros
  /StandingWaves/Flash/standwave.html