Chp 17.1 - Mechanical Waves

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Chp 17.1 - Mechanical Waves

• Pg. 500-503

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Mechanical Waves

• Mechanical Wave a disturbance in matter that
  carries energy from one place to another
• Medium - the material through which a wave
  travels
• Solids, liquids, and gases can all act as mediums
• Mechanical waves require a medium (or matter) to
  travel through. They cannot travel through empty
  space
• In a wave pool, waves travel through the water
  and carry energy across the pool. The water is
  the medium.

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Mechanical Waves

• A mechanical wave is created when a source of
  energy causes a vibration to travel through a
  medium
• Vibration is a repeating back and forth motion
• When you shake a rope, you add energy at one end,
  and the wave that results is a vibration that
  carries along the rope. The rope is the medium

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Types of Mechanical Waves

• The three main types of mechanical waves are
• Transverse waves
• Longitudinal waves
• Surface waves

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Wave Parts

• Crest - the highest point of the wave above the
  rest position
• Trough - the lowest point below the rest position
• Wavelength - the distance between a point on one
  wave and the same point on the next cycle of the
  wave
• Amplitude - the maximum displacement of the
  medium from its rest position

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Transverse Wave

• A wave that causes the medium to vibrate at right
  angles to the direction in which the wave travels
• When you shake one end of a rope the vibration
  causes a wave. Notice the wave carries every from
  left to right, in a direction perpendicular to
  the up- and-down motion of the rope

900
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Longitudinal Wave

• A wave in which the vibration of the medium is
  parallel to the direction the wave travels
• The vibration is a back-and-forth motion in the
  same direction or parallel to the direction in
  which the wave moves
• Compression - area where the particles in a
  medium are spaced close together
• Rarefaction - area where the particles in a
  medium are spread out

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Longitudinal Waves

• Examples
• Waves in a slinky or spring
• Primary waves (P waves) - longitudinal waves
  produced by earthquakes
• P waves travel through the earth. Scientists can
  use these waves to map Earths interior

Click this image to see animation
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Surface Waves

• A wave that travels along a surface separating
  two media
• Occurs when the up-and-down motion and the
  back-and-forth motions of transverse and
  longitudinal waves combine creating a circular
  motion (in deep water). Does not cause movement
  of debris.
• As a wave enters shallow water, the bottom of the
  wave slows because of friction and the top of the
  wave continues moving at the same speed. This
  causes the wave to topple over on itself or
  break. Breaking waves can carry debris to
  shore.

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The End

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