WAVESWAVES

WAVESWAVES

Carries energy from one place to another Carries energy from one place to another Classified byClassified by what what they move through they move through

1.1. Mechanical WavesMechanical Wavesthe energy is transferred by vibrations of medium the energy is transferred by vibrations of medium (medium = matter)(medium = matter)ex/ ocean waves move through waterex/ ocean waves move through water

2.2. Electromagnetic waves (EM Waves)Electromagnetic waves (EM Waves)the energy moves through disturbances in the the energy moves through disturbances in the electromagnetic field. No medium necessary.electromagnetic field. No medium necessary.

a disturbance that transfers energy

MECHANICAL WAVESMECHANICAL WAVESClassified by how medium vibrates

Longitudinal Waves:Vibration is in the same direction as

wave pulse (parallel to wave pulse)Ex: sound, some earthquake waves

Transverse Waves:Vibration is at 900 (right angles) to wave pulseEx: light, some earthquake waves

Surface Waves:Vibration is circular Ex: Ocean waves; surface waves

WAVE STRUCTUREWAVE STRUCTURE

CREST (peak)AMPLITUDEresting to max peak

WAVELENGTH

TROUGH

CHARACTERISTICS OF WAVESCHARACTERISTICS OF WAVES

Waves are described according Waves are described according to their to their

AmplitudeAmplitudemeasures DISPLACEMENTmeasures DISPLACEMENTsize of the disturbancesize of the disturbance

Wavelength Wavelength distance of a “repeating unit”distance of a “repeating unit”Also called a cycleAlso called a cycle

Velocity Velocity vv speed = how fast wave travelsspeed = how fast wave travels

AMPLITUDEAMPLITUDE

Distance between “rest & crest” or “rest & trough”Distance between “rest & crest” or “rest & trough”

Gives indication of “power” Gives indication of “power” or “strength” of waveor “strength” of wave(magnitude of earthquake = (magnitude of earthquake = Richter scale)Richter scale)

Determines loudness Determines loudness

(sound) or brightness(sound) or brightness

(EM wave)(EM wave)

WAVELENGTH WAVELENGTH Distance between any two Distance between any two

repeating points on a waverepeating points on a wave

crest-crest, crest-crest, trough-trough,trough-trough,expansion-expansion, expansion-expansion, compression-compressioncompression-compression

Determines what colorsDetermines what colorswe see; what notes we hear (pitch)we see; what notes we hear (pitch)

Shorter wavelengths have more Shorter wavelengths have more cycles per minute because they cycles per minute because they aren’t as longaren’t as long

Frequency Frequency ƒƒ

measured in measured in wavelengths/second or wavelengths/second or cycles/secondcycles/second

HertzHertz (Hz) = number of (Hz) = number of wavelengths in 1 secondwavelengths in 1 second

Frequency is related to Frequency is related to velocity:velocity: v v = = ƒ ƒ

How oftenHow often number of wavelengths that pass any point per secondnumber of wavelengths that pass any point per second

LONGITUDINAL WAVESLONGITUDINAL WAVES

Back and forth (compression & rarefraction)Back and forth (compression & rarefraction)

Also called compression or pressure waveAlso called compression or pressure wave

Wavelength is from compression to compressionWavelength is from compression to compression

or rarefaction to rarefaction or rarefaction to rarefaction

Vibration is parallel to the direction of the motion of the wave

Rarefraction (expansion)

Compression

VELOCITY VELOCITY vv the rate at which the the rate at which the

energy travelsenergy travels; ; speed & directionspeed & direction

Depends on mediumDepends on medium Mechanical waves travel Mechanical waves travel

faster through dense faster through dense mediumsmediums

EM Waves are faster EM Waves are faster through less dense through less dense mediumsmediums

If same medium, which is faster?

What can What can SoundSound waves do? waves do?

Waves can Waves can reflecreflect t (bounce)(bounce)

EchoesEchoes

Waves can Waves can refractrefract (bend)(bend)

Slight amplifications Slight amplifications (mostly over water)(mostly over water)

What can What can SoundSound waves do? waves do?

Waves can Waves can diffract diffract

(scatter)(scatter)

Ability to hear around Ability to hear around corners, through corners, through doors, etc.doors, etc.

The Doppler EffectThe Doppler Effect

The Doppler Effect ApplicationsThe Doppler Effect Applications

For LightFor Light

For SoundFor Sound

For WaterFor Water

Properties of SoundProperties of Sound

Loudness Loudness controlled by controlled by amplitude (dB)amplitude (dB)

Pitch controlled by Pitch controlled by frequency (Hz)frequency (Hz)

Speed controlled Speed controlled by mediumby medium