Waves

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Waves
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What is a Waves?

• A wave is a disturbance that transfers energy
  through matter or space.
• When waves move through matter, we call the
  matter a medium. A medium can be solid, liquid,
  or gas.
• Transverse waves can move through empty space
  without a medium.

• When energy waves move through a medium, the
  medium stays in the same place.
• In the ocean, when a wave passes, the water
  molecules move only in small circles!

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Types of Waves Transverse

• A wave in which the medium moves at right angles
  to the direction of the wave is a transverse
  wave.
• Ocean waves and light waves are transverse.

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Parts of a Transverse Wave

• The crest is the highest point of a transverse
  wave, and the trough is its lowest point.
• One wavelength includes one complete crest plus
  one complete trough

• The amplitude of a transverse wave in the
  distance from the normal to a crest or from the
  normal to a trough.
• The more energy a wave has, the greater the
  amplitude

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Types of waves longitudinal

• A longitudinal wave has the medium move parallel
  to the direction of the wave.
• Unlike transverse waves which can travel in empty
  space a longitudinal waves must have a medium to
  travel through.

• Sound travels in longitudinal waves.
• Because sound is a longitudinal wave , sound will
  not travel in empty space.

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Parts of a Longitudinal Wave

• The part of a longitudinal wave where the
  particles of the medium are close together is a
  compression.
• The part of a longitudinal wave where the
  particles of the medium are far apart is a
  rarefaction.

• One wavelength includes one complete compression
  plus one complete rarefaction.

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Wave properties

• For a transverse wave, the distance from crest to
  crest or trough to trough is a wavelength.
• For a longitudinal wave, a wavelength is the
  distance between compressions or between
  rarefactions.It is measured in meters.

• When you talk about a big wave, you are
  describing the waves amplitude.
• If you describe how many waves pass in a given
  time, you are describing the waves frequency.

• amplitude

wavelength
wavelength

• rarefaction

compression
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Wave amplitude

• If you are observing transverse waves, the
  amplitude is the vertical distance from the line
  of origin and the crest OR the line of origin and
  the trough.

• As you increase a waves energy, its amplitude
  also increases.

High amplitude

• Low
• amplitude

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Wave frequency

• The frequency of a wave is the number of waves
  that pass a point in a given time.
• Low frequency

• The unit for frequency is the Hertz, which means
  waves per second.
• High frequency

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Wave speed

• Wave speed measures how fast a wave is moving
  toward you.
• Wave speed frequency x wavelength
• The unit used to measure wave speed is meters per
  second.

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Math Problems with Waves

• Speed frequency x wavelength

Speed Freq.
wavelength
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Complete the practice problems
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Wave interactions Energy and change

• When a wave interacts with another wave or with
  an object, the amount of energy in the wave
  changes.
• The change in energy affects the waves
  properties.

• Wave properties include, its amplitude, speed,
  frequency or wavelength which may change.
• Wave interactions affect all wave types.
• Other changes that may happen are a change in
  wave direction, or the wave may break apart and
  then re-form.

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Wave interactions wave reflection

• Reflection happens when a wave bounces off of a
  surface.

• The angle of the incoming (incident) wave equals
  the angle of the outgoing (reflected) wave.

Normal
Angle of incidence
Angle of reflection
incident wave

• reflected wave

This is called the Law of Reflection
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Wave Interactions Refraction

• Waves can change speed when they pass from one
  medium to another.
• Sounds travel fastest in solids and slower in
  air.
• Sound is slowest in mediums like air and does not
  travel in a vacuum.

• Light travels fastest in a vacuum, gas, and even
  slower through a liquid, and even slowest through
  a solid like glass.
• Refraction is the bending of a wave as it passes
  through a medium.

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Wave interactions refraction Pt2
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Wave interactions diffraction

• The bending of a wave as it contacts the edge of
  a barrier is called diffraction.

• When waves are diffracted at the edge of a
  barrier, their wavelengths and frequencies do not
  change.

• Incoming wave crests

• outgoing wave crests

Diffraction allows you to hear around corners and
diffraction glasses split light into colors of
the rainbow
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Wave interactions interference

• The effect of two or more interacting waves is
  interference.
• There are 2 types of interference constructive
  and destructive.
• When two crests meet, the result is a larger
  wave. This is constructive interference. A tidal
  wave such as a tsunami is caused by constructive
  interference ! ! !

Constructive Interference
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• When a crest and a trough meet, the result is a
  smaller wave. This is destructive interference.

• In some auditoriums destructive interference
  makes it difficult to hear what is on stage.

Destructive Interference