Mechanical Waves

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Mechanical Waves
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What are waves?

• Wave a disturbance that transfers energy from
  place to place.
• Medium the material thru which a wave passes
• Waves travel trough the medium without actually
  moving the medium with it.

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Two Categories of Waves

• Mechanical
• These are waves that transfer energy through
  matter
• They require a medium (Solid, liquid, or gas)
• Examples of Mechanical Waves
• Transverse and Longitudinal waves

• Electromagnetic
• These are waves that transfer energy through a
  field
• They do NOT require a substance to travel through
• Examples of Electromagnetic Waves Microwaves and
  Cellular Phones

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Types of Mechanical Waves Transverse Waves
waves that move the medium at right angles to
the direction in which the waves are traveling.
Longitudinal Waves move particles parallel to
the direction the wave is moving, push-pull
waves.
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Wave Particle Movement

• Waves travel trough the medium without actually
  moving the medium with it. Basically the medium
  stays put while the wave moves some distance.

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How do we know waves carry energy and not matter?

• Think about an earthquake.
• When seismic waves travel through an area, the
  ground shakes from side to side and up and down,
  but the ground itself does not travel over a
  distance.
• Only the ENERGY moves!

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Properties of Waves Amplitude in a
transverse wave the height away from the rest
position. The amplitude in a longitudinal wave is
the measure of how compressed or rarefied the
medium becomes. Wavelength the distance
between two corresponding parts of a wave.
Frequency the number of complete waves that
pass a given point in a certain period of time.
Frequency is measured in HERTZ, one Hz is a wave
that occurs once every second.
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So what makes a wave?
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Longitudinal waves create points called
compressions and rarefactions.

• Compressions parts where the coils are close
  together
• Rarefactions parts where the coils are spread
  out

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What causes waves?

• You MUST have energy.
• Mechanical waves are produced when a source of
  energy causes a medium to vibrate.
• A vibration is a repeated back-and-forth or
  up-and-down motion.
• When a vibration moves through a medium, a wave
  results.

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Examples
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How do we calculate WAVE SPEED?
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Waves can also be reflective and refractive

• Waves can bounce off of something after striking
  it. That is a reflection. Sound and light waves
  can equally be reflective in nature and bounce
  energy wave back with equal force.
• Example) screaming in a canyon

• There are also times waves can not bounce back.
  Waves can bend at a different angle and refract.
  This occurs when wave energy is travel at a
  different speed than the medium.

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Interactions of Waves Diffraction Wave
passing a barrier or going through a hole in a
barrier bends and causes the wave to wrap around
the barrier.
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Vocabulary
Medium Wave Reflection Refraction Amplitude Compre
ssion Crest Longitudinal Rarefaction
Transverse Trough Wavelength Frequency Mechanic
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