Waves!

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Waves!

• Chapter 13

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13.1 Special Wiggles Vibrations and Waves

• When something moving back and forth, side to
  side, or up and down we say it vibrates.
• When that vibration moves through space and time
  we call it a wave.
• Waves are rhythmic disturbances that carry energy
  through matter or space

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13.1 Special Wiggles Vibrations and Waves

• Light and Sound both travel as a wave but they
  are two very different types of wave.
• Sound requires matter to move through to
  transport energy from one place to another
• Light can travel through space with out any
  matter to move through.
• It can even pass through many materials

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13.1 Special Wiggles Vibrations and Waves

• Wave Characteristics

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13.1 Special Wiggles Vibrations and Waves
A Resting point this is where the wave starts
from.
B Crest this is the highest point of the wave.
C Wavelength (?) the distance from one crest to
the next one
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13.1 Special Wiggles Vibrations and Waves
D Wavelength wavelength can also be the
distance between any two identical parts of the
wave
E Amplitude the distance from the resting point
to the crest.
F Amplitude amplitude can also be the distance
from the resting point to the trough
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13.1 Special Wiggles Vibrations and Waves
G Trough the lowest point of the wave
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13.1 Special Wiggles Vibrations and Waves

• Frequency How often the wave or vibration
  passes a point in one second.
• The symbol for frequency is f
• The unit for frequency is hertz (Hz)
• One hertz is one vibration per second

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13.1 Special Wiggles Vibrations and Waves

• Period The time it take for one complete
  vibration or one complete wave (crest and trough)
  to pass a point.
• The symbol for period is T.
• Think of is as a special unit of time
• The unit for period is seconds

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13.1 Special Wiggles Vibrations and Waves

• Period can be calculated from frequency and
  vis-versa
• Suppose a 2 waves passes a pole every second.
  This would make the frequency 2 Hz.
• This means the period of the wave is ½ seconds or
  a half a second.
• It takes a half a second for one complete wave to
  cycle through

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13.2 Wave Motion Transporting Energy

• When a wave moves through matter it carries
  energy
• It does not, however, carry the matter with it.
• A wave moving past a bobber moves the bobber up
  and down but does not move it in the direction of
  the wave.
• You dont feel sound waves from someone speaking
  because the air that is carrying the sound is not
  moving to you.

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13.2 Wave Motion Transporting Energy

• Because waves move we often need to know the wave
  speed.
• Wave speed is related to the frequency and the
  wavelength of the wave.
• Remember speed is

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13.2 Wave Motion Transporting Energy

• Wavelength is measured in meters which is the
  distance between the crests of the waves
• Frequency is equal to
• And Period is measured in seconds which is the
  time for one wave to complete its cycle or one
  wavelength to pass
• Wave speed is measured just like any other speed
  in m/s

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13.2 Wave Motion Transporting Energy

• Try it!
• A wave travels past the bird 3 time every second.
  It has a wavelength of 1 meter. What is the
  wave speed?

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13.2 Wave Motion Transporting Energy

Wavelength 1 m f 3 Hz
Wave speed
Wave speed wavelength x frequency
Wave speed 1m x 3 Hz
Wave speed 3 m/s
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13.3 Two types of waves Transverse and
Longitudinal

• Transverse Waves
• The medium vibrates in a perpendicular direction
  of the vibrating source
• Describing Transverse waves
• Crests the highest point of the wave
• Troughs the lowest points of the wave
• Wavelength the distance from crest to crest
• Amplitude the distance from the crest to the
  resting position
• Frequency the number of wave crests that pass a
  certain point each second.
• Examples
• Light
• Water Waves
• Waves in a guitar string

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13.3 Two types of waves Transverse and
Longitudinal

• Longitudinal Waves
• The medium vibrates in the same direction as the
  vibrating source
• Describing Longitudinal Waves
• Compression the dense area of the wave
• Rarefaction the less dense area of the wave
• Wavelength One compression and one rarefaction
• Frequency The number of compressions that pass
  a point each second.
• Examples
• Sound

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13.3 Two types of waves Transverse and
Longitudinal
A Longitudinal Wave B Transverse Wave