# Waves

Different kinds of waves and other information

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• Created by: Rachel
• Created on: 08-04-09 18:35

## Different types of waves

• Transverse- Propagation (direction of movement) perpendicular to oscillation eg a sine curve.
• Longitudinal- propagation parallel to direction of oscillation
• Mechanical- Require a medium to travel through
• Electromagnetic- Do not require a medium to travel through- can travel through a vacuum
• Plane waves- are straight
• Circular waves- in circles, spread out
• Pulse- A short section of wave, no repeated up and down motion
• Continuous wave- a model used by physicists to ensure they are modelling the middle of a plane wave. Do not exist in reality.
• Wave trains- have a beginning and an end
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## Wave information

• Wavelength = distance between two "equal" points on a wave eg crest to crest
• Frequency = number of waves per second
• Time period = time taken for one wavelength to pass a point
• Velocity = velocity of the wave
• V=fw
• f=1/T and T=1/f
• V=w/T
• Amplitude = greatest distance from the equilibrium position (maximum displacement)
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## Superposition

• Points on a wave that are a whole wavelength apart are in phase
• Points half a wavelength apart are in antiphase
• Principle of Superposition: when more than one wave meets in one place, the total displacement from the equilibrium position is the sum of the displacements of all the waves
• Must take into account the direction of displacement
• Applies to all waves
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## Stationary Waves

• Are caused when a wave is reflected back from a hard object or, for example, a string is tied at two points- superposition leads to the formation of a "stationary wave"
• The amplitude must be 0 at both ends for string tied at both ends, so w=2l/n
• l=length of string
• n=an integer... 1,2,3... etc
• w=wavelength
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