Wave
Transfer of energy through a medium by a disturbance.
Disturbance can be repeating or a single event.
Only medium is disturbed, energy is only seen in disturbance.
Medium ­ substance or material through which a wave travels. Energy moves by causing a disturbance in the medium that propagates or travels through the material by movement of the medium atoms.
Oscillation vs. Propagation What is the difference?
Oscillation ­ motion that repeats in a regular cycle or time period. A sine curve shape is produced by the oscillation.
Propagation ­ Transfer of energy through a medium from point to point. Energy transfers by particle vibrations
http://illuminations.nctm.org/tools/soundwave/
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Pulses
vs
Pulse ­ a short disturbance
Periodic Waves
Periodic Waves ­ continuous oscillation driven by a repetitive driving force
http://phet.colorado.edu/sims/wave­on­a­
string/wave­on­a­string_en.html
Categories of Waves
Mechanical Waves ­ Caused by a disturbance of a medium by a vibration.
Require a physical medium to transfer through.
Speed is dependent on medium density and wave shape.
Can be transverse or longitudinal. Example :
Electromagnetic Waves ­ Transfer of energy through a vacuum. There is no 'physical' medium needed.
A vibration of either the electric or magnetic fields. Can only be a transverse wave.
Example:
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Electromagnetic Spectrum
What are some basic measurements used for describing waves?
Wavelength ­
Frequency ­
Amplitude ­ Period ­
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What are the parts of a wave?
Types of Wave
Waves are characterized by both what
they move through and how their energy
disturbs the medium they transmit
through.
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Types of Waves
Transverse Energy causes disturbance in medium
perpendicular to direction of travel.
Types of Waves
Longitudinal WavesEnergy causes disturbance in medium parallel to
direction of wave travel.
- usually created when a substance
vibrates back and forth.
Longitudinal waves do not have
crest and troughs
They have regions of:
compression and rarefaction.
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How do you calculate the speed of a wave?
Wave speed is determined by the medium
• Sound waves travel fastest in a solid, then liquid, then gas
• Mechanical waves travel as fast as they can disturb the next particle (solid particles are closer together)
• Speed of light (EM waves) in a vacuum: c = 3.0 x 108 m/s
• Light is slowed down slightly by water, air, or other matter.
Speeds of sound What does the speed of the wave depend on?
Trends of Temperature:
•
•
•
•
•
•
Air at 25 degrees Celsius 346 m/s
Hydrogen at 0 degrees Celsius 1290 m/s
Sea water 1530 m/s
Copper 3560 m/s
Aluminum 5100 m/s
Iron 5130 m/s
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