Chapter 11 Section 3 Notes

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Chapter 11 Section 3 Notes

• Wave Interactions

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Reflection

• Reflection the bouncing back of a wave as it
  meets a surface or boundary.
• Example When light hits a shiny bumper it
  reflects back off of it.

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Reflection

• When a boundary is free to move, the reflected
  wave is exactly like the original wave.

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Reflection

• When a boundary is fixed (doesnt move), the
  reflected wave is like the original, but turned
  upside down and travels in the opposite
  direction.

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Diffraction

• Diffraction the bending of a wave as it passes
  an edge or opening.

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Diffraction

• Example A person standing in a hallway is able
  to hear voices coming from a classroom because
  the sound waves bend as they pass the opening of
  the door.

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Refraction

• Refraction the bending of waves as they pass
  from 1 medium to another

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Refraction

• The waves reflected from the bottom of the spoon
  reach your eyes from a different angle than the
  waves at the top of the spoon.

• Example A spoon in a glass of water looks bent
  because of refraction. The light waves bend as
  they pass from the air to the water to your eyes.
  Each time the waves enter a new medium, they bend
  because of a change in wave speed.

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Interference

• Interference the combination of 2 or more waves
  that exist in the same place at the same time and
  result in a single wave

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Interference

• Constructive Interference any interference in
  which waves combine so that the resulting wave is
  larger than the original wave.
• Diagram of constructive interference

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Interference

• Destructive Interference any interference in
  which waves combine so the resulting wave is
  smaller than the largest of the original wave.
• Diagram of destructive interference

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Interference of Light Waves

• Why do bubbles have a swirling rainbow effect?
• Some waves bounce off the outside of the bubble
  and travel directly to your eye, while other
  waves travel into the thin shell of the bubble
  and bounce off the inner side of the bubbles
  shell, then back through the shell, air, and your
  eye. At times, the 2 sets of waves are out of
  phase with each other. They interfere
  constructively at some frequencies (colors) and
  destructively at other frequencies (colors).

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Interference of Sound Waves

• When compressions from 2 sound sources arrive at
  your ear at the same time, constructive
  interference occurs and the sound is louder.
• A short time later, a compression from one source
  and a rarefaction from the other arrive together,
  destructive interference occurs and a softer
  sound is heard.
• You hear a pattern of alternating loud and soft
  sounds, called beats.

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Standing Waves

• Standing Waves a wave caused by interference
  that appears not to move along the medium and
  that shows some regions of no vibration (nodes)
  and other regions of maximum vibration (antinodes)

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Standing Waves

• Nodes Points that have no vibration
• They are located at points where crests of
  original waves meet the troughs of reflected
  waves
• Antinodes Point that have maximum vibrations
• They are formed where crests of original waves
  line up with crests of reflected waves and
  constructive interference occurs

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Standing Waves Diagram
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Key Ideas

• What happens when a wave meets an object?
• What happens when a wave passes into another
  medium?
• When a wave meets a surface, the wave bounces
  back. That is called REFLECTION.
• When a wave passes the edge of an object or
  passes through an opening, the wave bends. That
  is called DIFFRACTION.
• A wave also bends when it passes from one medium
  to another at an angle. That is called
  REFRACTION.