03-03-08 - waves
TRANSCRIPT
WaveWaveare oscillations (repeating are oscillations (repeating disturbance or movement) disturbance or movement)
that that transfers energytransfers energy through through mattermatter or or spacespace..
Waves move due to the Waves move due to the movementmovement
of a of a vibrationvibration
from a from a sourcesource
through a through a mediummedium
longitudinal or compressional
transverse
pulse (single event)continuous (repeated events)
Physical matter for mechanical waves
Electric and magnetic fields for electromagnetic waves
Classification of Waves
Mechanical
Electromagnetic
Longitudinal
Transverse
Surface
Classification according to medium through which wave travels
Classification according to wave orientation
Light, radio, x-rays, and gamma raysLight, radio, x-rays, and gamma raysare some examples of e/m waves. are some examples of e/m waves.
Electric & magnetic fields are needed forElectric & magnetic fields are needed forELECTROMAGNETICELECTROMAGNETIC waves.waves.
Mechanical WavesThere are 3 types of mechanical waves.
– 1) transverse waves – 2) compressional waves or longitudinal waves– 3) surface waves
Electromagnetic Waves
Mechanical Waves
• Matter is the medium
• Sound is a mechanical wave
Electromagnetic Waves
• Electric and magnetic fields are the media
• Light is an electromagnetic wave
The displacement of the particlesThe displacement of the particlesof the medium isof the medium is perpendicularperpendicular totothe direction of wave propagation.the direction of wave propagation.
TRANSVERSETRANSVERSE
LONGITUDINALLONGITUDINAL
The displacement of the particlesThe displacement of the particlesof the mediumof the medium isis parallelparallel to theto thedirection of wave propagation.direction of wave propagation.
Longitudinal • Longitudinal wave has
oscillations that travel parallel (same direction) to the direction of motion
• Made up of compressions and rarefactions in the medium that they are traveling in
• Examples: sound waves and s waves for earthquakes
Transverse Waves
• All electromagnetic waves are transverse. This includes light.
• Transverse wave: has its oscillations perpendicular to the direction of the wave. The wave moves left to right and the oscillation moves up and down
Click here, here, and hereto view simulations of
transverse and longitudinal waves.
SURFACESURFACE
A A combinationcombination of oftransverse transverse and and longitudinallongitudinal..
Ocean waves are an example of surface waves
Properties of Waves
• The properties of a waveforms are:
• wavelength (period)
• amplitude
• velocity
• frequency
• All periodic (repeating) waveforms have these common characteristics
WavelengthWavelengththe horizontal the horizontal distancedistance of of
one complete wave (crest to one complete wave (crest to crest or trough to trough)crest or trough to trough)
denoted by denoted by and measured in units of length (m) and measured in units of length (m)
AmplitudeAmplitudethe the maximum displacementmaximum displacement
of a particle of the medium fromof a particle of the medium fromthe rest or equilibrium positionthe rest or equilibrium position
denoted by A and measured in units of length (m)denoted by A and measured in units of length (m)
FrequencyFrequency- - the number of waves the number of waves that pass a given point in one secondthat pass a given point in one second
denoted by f and measured in units of Hzdenoted by f and measured in units of Hz
PeriodPeriod - - the shortest the shortest timetime interval during interval duringwhich the motion of the wave repeats itselfwhich the motion of the wave repeats itself
denoted by T and measured in units of time (s)denoted by T and measured in units of time (s)
T = 1/f
& f = 1/T
VelocityVelocity - the - the speedspeed of the wave of the wave
denoted by v and measured in units of dist/time (m/s)denoted by v and measured in units of dist/time (m/s)
v = d/t = /T = f
The speed of a wave depends on the propertiesThe speed of a wave depends on the propertiesof the medium through which it is traveling.of the medium through which it is traveling.
InterferenceInterferencethe result of the the result of the superpositionsuperposition
of two or more wavesof two or more waves
Superposition PrincipleSuperposition Principle
the displacement of the medium whenthe displacement of the medium whentwo or more waves pass throughtwo or more waves pass through
it at the same time is the it at the same time is the algebraicalgebraicsumsum of the displacements caused of the displacements caused
by the individual wavesby the individual waves
ConstructiveConstructiveresults in a larger amplitudelarger amplitude
Types of InterferenceTypes of Interference
DestructiveDestructiveresults in a smaller amplitudesmaller amplitude
ReflectionReflection
the the turning backturning back of a wave when of a wave whenit reaches the it reaches the boundaryboundary of the of the
medium through which it is travelingmedium through which it is traveling
Law of ReflectionLaw of Reflection
the the angle of incidenceangle of incidence is is equalequalto the to the angle of reflectionangle of reflection
There are two types of reflection.
Fixed-end TerminationFixed-end Terminationthe reflected wave is
inverted when it reflectsfrom a more dense medium
Free-end TerminationFree-end Terminationthe reflected wave is
upright when it reflectsfrom a less dense medium
Click Click here to view these types of reflection.
the bendingbending of a wave as it passes obliquelyobliquely from
one medium into another of different propagation different propagation
speedspeed
RefractioRefractionn
For refraction to occur, the waveFor refraction to occur, the wavemust change speed and must entermust change speed and must enterthe new medium at an oblique angle.the new medium at an oblique angle.
DiffractionDiffractionthethe spreadingspreading of a of a
wavewavearound a barrier oraround a barrier orthrough an openingthrough an opening
Read more about interference Read more about interference here.
Click Click here to view the interferencepattern resulting from the superpositionpattern resulting from the superposition
of two transverse waves.of two transverse waves.
Click Click here and here to viewsimulations of the interference of
two circular waves.
A standing wavestanding wave is theresult of two wave trains of the same
wavelength, frequency, and amplitudetraveling in opposite directions
through the same medium.
Learn more about standing waveshere, here, and here.
Click here to view a simulation of theinterference of two traveling wavesthat can result in a standing wave.
Click here to view a simulationof standing waves on a string.
Standing waves may be produced easily inwater, string, and air columns.
Doppler EffectDoppler Effectthe change in frequency due to the relativethe change in frequency due to the relativemotion of the wave source and the observermotion of the wave source and the observer
The The observed frequencyobserved frequency is is higherhigher when when thethe
source and observer are getting source and observer are getting closercloser..
The The observed frequencyobserved frequency is is lowerlower when when thethe
source and observer are getting farther source and observer are getting farther awayaway..
Click Click here, here, here, and hereto run simulations of the Doppler Effect.to run simulations of the Doppler Effect.
The Doppler EffectThe Doppler Effectcan be evident forcan be evident forall types of waves –all types of waves –including light,including light,sound, water, etc…sound, water, etc…