An Introduction to Waves

1
An Introduction to Waves
2
What is a wave?

• Waves are disturbances that transmit energy
  through matter or empty space
• Which types of waves have we already discussed
  can transmit energy through empty space?
• Electromagnetic waves (radiation)
• What are some of the waves present in the room
  right now?
• Light waves, sound waves, water waves

3
Types of waves

• All waves transfer energy through vibrations
• Waves can be classified by the direction the
  particles of the medium vibrate versus the
  movement of the wave
• Two main types of waves
• Transverse and
  longitudinal

4
Transverse waves

• Waves that cause particles to vibrate up and down
• Particles move perpendicularly to the direction
  that the wave is moving

5
Longitudinal waves

• The particles of the medium vibrate back and
  forth along the path of the wave movement

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• A waves amplitude is related to its height
• It is the max. distance the particles of a medium
  vibrate from their rest position
• The rest position is where the particles are when
  there is no disturbance
• The green arrows show the amplitude of this wave
• What does a large amplitude tell you about the
  waves height?

7

• Why do you have to work harder to create a large
  amplitude than you do to create a smaller
  amplitude?
• Because it requires more energy to move the
  medium farther from its rest position
• So, waves with larger amplitudes carry more
  energy than waves with smaller amplitudes
• Remember that a wave is a disturbance that
  carries energy

A
B
8
Parts of a wave

• The crest of a transverse wave is found at the
  highest point of the wave
• The trough of a transverse wave is found at the
  lowest point of the wave

Crest
trough
9
Parts of a wave part II

• The compressions of a longitudinal wave are found
  where the mediums particles are closest together
• The rarefactions of a longitudinal wave are found
  where the mediums particles are farthest apart

10

• The wavelength of a wave is the distance between
  any two crests or compressions next to each other
• It can also be measured between two troughs or
  rarefactions
• A shorter wavelength carries more energy than a
  longer wavelength

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• The number of waves produced in a given amount of
  time is the frequency of the wave
• Usually given in hertz (Hz)
• One hertz is equal to one wave per second
• High frequency waves carry more energy than low
  frequency waves if the amplitude is the same