This is one type of wave…. wave Wave a disturbance that propagates through a material medium or space. Waves transfer energy without the bulk transport.

This is one type of This is one type of wave….….

WaveWavea a disturbance disturbance that propagatesthat propagates

through a material through a material mediummedium or or spacespace..

Waves Waves transfer energytransfer energy without withoutthe bulk transport of matter.the bulk transport of matter.

In order for a In order for a mechanical wavemechanical wave to to exist, exist, energyenergy is needed to create is needed to create

a a disturbancedisturbance in an in an elastic elastic mediummedium..

WaveWave

On the nature of waves: "A wave of people in a On the nature of waves: "A wave of people in a stadium is a true example of a wave. The disturbance stadium is a true example of a wave. The disturbance consists of the people removing themselves from consists of the people removing themselves from their seated positions, standing up, and sitting down their seated positions, standing up, and sitting down again. That disturbance moves around the stadium, again. That disturbance moves around the stadium, and it carries with it the energy that it takes to lift a and it carries with it the energy that it takes to lift a person out of his or her seat—but it does not move person out of his or her seat—but it does not move the people around the stadium. A wave, then, is a the people around the stadium. A wave, then, is a traveling disturbance that carries energy, but it traveling disturbance that carries energy, but it doesn’t carry matter." doesn’t carry matter."

WaveWavea a disturbance disturbance that propagatesthat propagates

through a material through a material mediummedium or or spacespace..

Waves Waves transfer energytransfer energy without withoutthe bulk transport of matter.the bulk transport of matter.

In order for a In order for a mechanical wavemechanical wave to to exist, exist, energyenergy is needed to create is needed to create

a a disturbancedisturbance in an in an elastic elastic mediummedium..

All EM wavesAll EM waves travel through freetravel through freespace at a speed of approximatelyspace at a speed of approximately

3.00 x 103.00 x 1088 m/s m/s oror 186,000 miles/sec 186,000 miles/sec..

This speed is known as theThis speed is known as the speed of light (c)speed of light (c)..

Light, radio, x-rays, and gamma raysLight, radio, x-rays, and gamma raysare some examples of EM waves. are some examples of EM waves.

No medium is needed forNo medium is needed forELECTROMAGNETICELECTROMAGNETIC waves.waves.

The Electromagnetic (EM) Spectrum

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.

Click here or hereto view simulations of

transverse and longitudinal waves.

SURFACESURFACE

A A combinationcombination of oftransverse transverse and and longitudinallongitudinal..

AmplitudeAmplitudethe the maximum displacementmaximum displacement

of a particle of the medium fromof a particle of the medium fromthe the restrest or or equilibriumequilibrium position positiondenoted by A and measured in units of lengthdenoted by A and measured in units of length

Wavelength (Wavelength (λλ))the the shortest distanceshortest distance

betweenbetweentwo points that are two points that are ““in phasein phase

””denoted by denoted by and measured in units of length and measured in units of length

(m or cm)(m or cm)

Frequency (f)Frequency (f)- - the number of the number of complete vibrations per unit timecomplete vibrations per unit time

A common unit is Hz (cycles/second)A common unit is Hz (cycles/second)

Period (T)Period (T) - - the shortest the shortest timetime interval during interval duringwhich the motion of the wave repeats itselfwhich the motion of the wave repeats itself

Measured in units of time (s or mins)Measured in units of time (s or mins)

&T

f1

f

T1

Velocity (v)Velocity (v) - the - the speedspeed of the wave of the wave

Measured in units of dist/time (m/s)Measured in units of dist/time (m/s)

The speed of a wave depends on the The speed of a wave depends on the propertiespropertiesof the mediumof the medium through which it is traveling. through which it is traveling.

f

t

dv

T

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. to view these types of reflection.

the bendingbending of a wave as it passes obliquelyobliquely from

one medium into another

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

DiffractionDiffractionExample: Sound waves spreading Example: Sound waves spreading as they go through a doorwayas they go through a doorway

-fuzzy edges of shadows-fuzzy edges of shadows

DiffractionDiffractionDiffraction effect (amount of Diffraction effect (amount of bending) is greatest when the bending) is greatest when the width of the gap is about the same width of the gap is about the same size as the wavelength of the wavesize as the wavelength of the wave

Try it Try it here

DiffractionDiffractionWhy do we care?.......Why do we care?.......

Diffraction accounts for the following phenomena:Diffraction accounts for the following phenomena:• Iridescent CloudsIridescent Clouds• RainbowsRainbows• Shadows with fuzzy edgesShadows with fuzzy edges• How sound can travel from one room to anotherHow sound can travel from one room to another

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

Applications of Standing Applications of Standing Waves….Waves….

Harmonics for Stringed Harmonics for Stringed instrumentsinstruments

Resonance in wind instrumentsResonance in wind instruments

Read more about interference Read more about interference here..

InterferenceInterference

You can view reflection,You can view reflection,refraction, diffraction,refraction, diffraction,and interference using bothand interference using bothplane and circular waves.plane and circular waves.

The ripple tankThe ripple tanksimulation foundsimulation foundhere can be used can be usedto investigateto investigatewave properties.wave properties.

Read more about wave interference Read more about wave interference here..

You can view reflection,You can view reflection,refraction, diffraction,refraction, diffraction,and interference using bothand interference using bothplane and circular waves.plane and circular waves.

The ripple tankThe ripple tanksimulation foundsimulation foundhere can be usedhere can be usedto investigateto investigatewave properties.wave properties.

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 waves 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 here, here, here, and hereClick here, here, here, and hereto run simulations of the Doppler Effect.to run simulations of the Doppler Effect.