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WAVESWAVES
Komang Gde SuastikaKomang Gde Suastika Physics DeptPhysics Dept Palangka Raya UniversityPalangka Raya University Email: suastika358@yahoo.comEmail: suastika358@yahoo.com
What do you know?
About waves?
TujuanTujuan
1. By the end of this lesson you will be able to:1. By the end of this lesson you will be able to:
State that a State that a wave transfers energywave transfers energy..
2. Use the following terms correctly in context: 2. Use the following terms correctly in context: wave, wave, frequency, wavelength, speed, amplitude, frequency, wavelength, speed, amplitude, periodperiod..
3. State the difference between a 3. State the difference between a Mechanical WavesMechanical Waves
and a and a Electromagnetic waves (EM Waves)Electromagnetic waves (EM Waves), and give , and give an example of each.an example of each.
4. State the difference between a 4. State the difference between a longitudinallongitudinal wave wave
and a and a transversetransverse wave, and give an example of each. wave, and give an example of each.
Perhatikan Fenomena berikutPerhatikan Fenomena berikut
WAVESWAVESa disturbance that transfers energy
Waves transfer energy…Waves transfer energy…
Waves transfer energy…Waves transfer energy…
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 distance of a ““repeating unitrepeating unit””Also called a cycleAlso called a cycle
Velocity Velocity vv speed = how fast wave travelsspeed = how fast wave travels
AMPLITUDEAMPLITUDE
Distance between Distance between ““rest & crestrest & crest”” or or ““rest & troughrest & trough””
Gives indication of Gives indication of ““powerpower”” or or ““strengthstrength”” of wave of wave(magnitude of earthquake = (magnitude of earthquake = Richter scale)Richter scale)
Does not affect Does not affect
velocity of wavevelocity of wave
Determines loudness (sound) or brightness (EM wave)Determines loudness (sound) or brightness (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 arenaren’’t as longt as long
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
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
PERIOD TPERIOD T
How longHow longAmount of time for one wavelength to pass a pointAmount of time for one wavelength to pass a point
Related inversely to frequencyRelated inversely to frequency
11 == 11
TT ff
PeriodPeriod == 11
FrequencyFrequency
Properties of WavesProperties of Waves
What is meant by the axis of a wave?What is meant by the axis of a wave?The axis is the line runningthrough the middle of thewave pattern.
What is meant by the crest of the What is meant by the crest of the wave?wave?
The crest is the top part of the wave
……and the trough?and the trough?
The trough is the bottompart of the wave.
What is the amplitude of the wave?What is the amplitude of the wave?
The amplitude is thedistance from the axis tothe crest
or from axis to trough.
Definition of Wavelength?Definition of Wavelength?The wavelength is thedistance after which thewave pattern repeats itself– the distance between twoidentical points on the wave
Wavelength is given the symbol λ pronounced lambda.
FrequencyFrequency
The frequency of the wave is the number The frequency of the wave is the number of waves each second.of waves each second.
It is measured in hertz (Hz) which justIt is measured in hertz (Hz) which just means means ““per secondper second””. .
FrequencyFrequency
Calculate the frequency of each of theCalculate the frequency of each of the
following waves:following waves:
125 waves passing a point in 10 seconds.125 waves passing a point in 10 seconds. 16 waves passing a point in 24 seconds.16 waves passing a point in 24 seconds. 30 waves passing a point in 1 minute.30 waves passing a point in 1 minute.
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.electromagnetic field.
WAVE STRUCTUREWAVE STRUCTURE
CREST (peak)AMPLITUDEresting to max peak
WAVELENGTH
TROUGH
MECHANICAL WAVESMECHANICAL WAVES
travel through & gradually lose energy to that medium
Examples:Examples: water, sound, rope, & water, sound, rope, &
spring wavesspring waves
Mechanical Media:Mechanical Media: water, air, rope, springwater, air, rope, spring
require a medium (the material through which the
disturbance is moving) to transmit energy
Making a pulse
MECHANICAL WAVESMECHANICAL WAVESClassified by how medium vibrates
Pulse = direction of energy transfer
Vibration = direction of vibration of medium relative to pulse
3 types: Longitudinal, transverse, surface
MECHANICAL WAVESMECHANICAL WAVESClassified by how medium vibrates
Longitudinal Waves:Vibration is in the same direction as
wave pulse (parallel to wave pulse)
Transverse Waves:Vibration is at 900 (right angles) to wave pulse
Surface Waves:Vibration is circular Ex/ Ocean waves; surface waves
TRANVERSE WAVESTRANVERSE WAVES
Sideways or up & downSideways or up & down Examples:Examples:
S-type earthquake wavesS-type earthquake waves Electromagnetic (EM) or Electromagnetic (EM) or
light waveslight waves
Vibration is perpendicular to the direction of the motion of the wave
LONGITUDINAL WAVESLONGITUDINAL WAVES
Back and forth (compression & rarefraction)Back and forth (compression & rarefraction)
Also called compression or pressure waveAlso called compression or pressure wave
Examples:Examples: P-type earthquake wavesP-type earthquake waves Sound wavesSound waves
Vibration is parallel to the direction of the motion of the wave
Rarefraction (expansion)
Compression
Waves describe the EarthWaves describe the Earth
S waves move through solids only!!!
P waves move through solids & liquidsP waves move through solids & liquids
Are these MECHANICAL WAVES????
YES!! Seismic waves need a medium (the earth!)
Penjalaran GelombangPenjalaran Gelombangdalam Satu Dimensidalam Satu Dimensi
Fungsi Gelombang :)( vtxfy
)( vtxfy
Menjalar ke kanan
Menjalar ke kiri
Cepat-rambat Gelombang (Kecepatan Fasa) : dt
dxv
Superposisi dan Interferensi Superposisi dan Interferensi GelombangGelombang
Gelombang Bunyi
Cepat-rambat Gelombang di dalam Cepat-rambat Gelombang di dalam DawaiDawai
F
v Tegangan dawai
Massa dawai persatuan panjang 2MLT F
1ML
1LT v
Refleksi dan Transmisi Gelombang
Rambatan gelombang dari medium kurang rapat ke medium yang lebih rapat
Rambatan gelombang dari medium lebih rapat ke medium yang kurang rapat
Harmoni GelombangHarmoni Gelombang
xAy
2
sin
A
vtxAy
2
sinUntuk Gelombang yangMenjalar ke kanan
Tv atau vT
Ttx
Ay
2sin
2k
T 2
tkxAy sin
vtxAy
2
sin
Tv
T
txAy
2sin
PERSAMAAN GELOMBANGPERSAMAAN GELOMBANG
x
x
f (x)t = 0
c t
f (x - ct)
Gelombang Sinusoidal Dalam Domain RuangGelombang Sinusoidal Dalam Domain Ruang
)2
(sin xAy
Amplitudo
x
A
Panjang gelombang
Bilangan gelombang
)(sin xkAy
x
Gelombang Sinusoidal Dalam Domain WaktuGelombang Sinusoidal Dalam Domain Waktu
)2
(sin tT
Ay
t
A
T
Perioda
Amplitudo
)(sin tAy )2(sin tfAy
Frekuensi sudut
Frekuensi
Dalam Domain Ruang Dan WaktuDalam Domain Ruang Dan Waktu
)(sin txkAy
Sebuah gelombang perpindahan dinyatakan dengan : (x,t) = 0,02 sin [ 2 ( 0,5 x – 10 t ) ] mTentukan panjang gelombang, frekuensi dan kecepatannya.
Contoh
Jawab :
)22
(sin)(sin),( tfxAtxkAtx
)105,0(2sin02,0)1
(2sin),( txtfxAtx
TcT
f1
m2
Hzf 10
smfT
c /20)10)(2(
Tugas Tugas Persamaan suatu gelombang yang bergerak Persamaan suatu gelombang yang bergerak transversal transversal
3001.02sin2
xty
Dimana x dan y dalam cm dan t dalam detik. Berapa amplitudo, panjang gelombang, frekuensi dan kecepatan rambat gelombang itu
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