Waves

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Waves
Sound Waves

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What Is a Wave?

• A disturbance
• Transmits energy not matter
• Through matter and space
• Medium-matter through which a wave travels
• Sound waves require a medium

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Waves Transfer Energy

• Waves can do work

• Examples
• Sand
• Eardrum

• Eye, photo film

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Sound

• When sound travels in the air, the waves spread
  out as spheres
• As they travel outward they get bigger

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Longitudinal Wave
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Vibrations of the drum head create sound waves in
the air
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Sound Waves Are Pressure Waves

• Pressure nodes appear symmetrically at each end
• Open to the atmosphere

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Standing Wave

• Fundamental frequency for each pipe
• Wavelength ? 2L
• Frequency f v / 2L
• Shorter the length higher the frequency

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Harmonics

• ? L
• f v / L
• Even numbered multiples of the fundamental

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Pitch

• Large wavelength -
• Low frequency -
• Low pitch
• Small wavelength -
• High frequency -
• High pitch

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Moving Sound Source

• As the source of a wave moves
• The wave fonts bunch up in front
• Spread out behind

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The Doppler Effect
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• What if the disturbance is traveling at the same
  speed as the wave fronts?

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• What if the disturbance is traveling faster than
  speed of the wave fronts?

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Bow Wave
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Bow Waves
Bow Wow Waves
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Period

• Time required for a full wavelength to pass
• Symbol is T
• SI unit is seconds

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Frequency

• Frequency measures the rate of vibrations

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Frequency

• Number of vibrations that occur in an 1 sec time
  interval
• Period the time required for one full
  wavelength to pass a certain point