Waves
description
Transcript of Waves
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WavesWaves
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The Nature of The Nature of WavesWaves
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What is in a wave?What is in a wave?
•A A wavewave is a repeating is a repeating disturbance or movement that disturbance or movement that transfers energy through matter transfers energy through matter or space.or space.
•For example, during earthquakes, For example, during earthquakes, energy is transferred in powerful energy is transferred in powerful waves that travel through Earth. waves that travel through Earth.
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Wave and EnergyWave and Energy•A pebble falls into a pool A pebble falls into a pool of water and ripples form. of water and ripples form.
•Because it is moving, the Because it is moving, the falling pebble has energy. falling pebble has energy.
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•As it splashes into the pool, As it splashes into the pool, the pebble transfers some of the pebble transfers some of its energy to nearby water its energy to nearby water molecules, causing them to molecules, causing them to move.move.
•What you see is energy What you see is energy traveling in the form of a traveling in the form of a wave on the surface of the wave on the surface of the water. water.
•RaftRaft
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• The waves don’t even carry The waves don’t even carry the water along with them. the water along with them. •Only the energy carried by Only the energy carried by the waves moves forward. the waves moves forward. •All waves have this propertyAll waves have this property
•They carry energy without They carry energy without transporting matter from place transporting matter from place to place. to place.
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Making WavesMaking Waves•A wave will travel only as A wave will travel only as
long as it has energy to carry. long as it has energy to carry. •Anything moving up and Anything moving up and
down or back and forth in down or back and forth in rhythm is vibrating. rhythm is vibrating.
•All waves are produced by All waves are produced by vibrating mattervibrating matter
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Mechanical WavesMechanical Waves•Some wave require matter to Some wave require matter to
transfer the energy.transfer the energy.•The matter the waves travel The matter the waves travel
through is called a through is called a mediummedium. . •The medium can be a solid, a The medium can be a solid, a
liquid, a gas, or a liquid, a gas, or a combination of these. combination of these.
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•The two types of The two types of mechanical waves are mechanical waves are transversetransverse waves and waves and compressionalcompressional waves. waves.
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Transverse WaveTransverse Wave• In a In a transverse transverse
wavewave, matter in the , matter in the medium moves back medium moves back and forth at right and forth at right angles to the angles to the direction that the direction that the wave travels. wave travels.
• For example, a For example, a water wave travels water wave travels horizontally as the horizontally as the water moves water moves vertically up and vertically up and down. down.
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Compressional Waves Compressional Waves •In a In a compressional wavecompressional wave, ,
matter in the medium moves matter in the medium moves back and forth along the same back and forth along the same direction that the wave travels.direction that the wave travels.
•The wave carries energy, but The wave carries energy, but not matter, forward along the not matter, forward along the spring.spring.
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•Compressional waves also Compressional waves also are called are called longitudinallongitudinal waves waves
•Sound creates Sound creates compressional waves.compressional waves.
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Deep Water WavesDeep Water Waves•A water wave causes water to A water wave causes water to
move back and forth, as well move back and forth, as well as up and down. as up and down.
•This motion causes both This motion causes both transverse and compressional transverse and compressional waveswaves
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Seismic WavesSeismic Waves• Forces in Earth’s crust can cause Forces in Earth’s crust can cause
regions of the crust to shift, bend, regions of the crust to shift, bend, or even break.or even break.
• The breaking The breaking crust vibrates, crust vibrates, creating seismic creating seismic waves that waves that carry energy carry energy outward. outward.
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•Seismic wavesSeismic waves are a are a combination of compressional combination of compressional and transverse waves. and transverse waves.
•They can travel through Earth They can travel through Earth and along Earth’s surface.and along Earth’s surface.
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Wave Wave PropertiesProperties
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The Parts of a WaveThe Parts of a Wave•Transverse wavesTransverse waves and and
compressional wavescompressional waves have have different characteristics: crests different characteristics: crests and trough, compressions and and trough, compressions and rarefactions.rarefactions.
•They also have similar properties: They also have similar properties: wavelength, frequency, period, wavelength, frequency, period, amplitude, and wave speed.amplitude, and wave speed.
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The Parts of a Transverse The Parts of a Transverse WaveWave•A transverse wave has alternating A transverse wave has alternating
high points, high points, crestscrests, and low , and low points, points, troughstroughs..
Rest Rest position is position is also called also called equilibriumequilibrium..
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Wavelength of Transverse Wavelength of Transverse WaveWave•A A wavelengthwavelength, , ,, is the distance is the distance
between one point on a wave between one point on a wave and the nearest point just like it.and the nearest point just like it. • Wavelength is Wavelength is
the distance the distance from crest to from crest to crest or crest or trough to trough to trough.trough.
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The Parts of a Compressional The Parts of a Compressional WaveWave•A compressional wave has A compressional wave has regions where the particles are regions where the particles are close together, close together, compressionscompressions..
•And regions And regions where the where the particles are particles are further apart, further apart, rarefactionsrarefactions..
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The wavelength of a The wavelength of a Compressional WaveCompressional Wave•A wavelength is the distance between A wavelength is the distance between
two neighboring compressions or two two neighboring compressions or two neighboring rarefactions.neighboring rarefactions.
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AmplitudeAmplitude•AmplitudeAmplitude is related to the is related to the
energy carried by a wave.energy carried by a wave. •The greater the wave’s amplitude The greater the wave’s amplitude
is, the more energy the wave is, the more energy the wave carries.carries.
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Amplitude of a Transverse Amplitude of a Transverse WaveWave•The The amplitudeamplitude is the distance from is the distance from
the crest or trough of the wave to the crest or trough of the wave to the rest position of the medium.the rest position of the medium.
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The Amplitude of a The Amplitude of a Compressional WaveCompressional Wave•The amplitude of a compressional The amplitude of a compressional
wave is related to how tightly the wave is related to how tightly the medium is pushed together at medium is pushed together at the compressions.the compressions.
•The denser the medium is at the The denser the medium is at the compressions, the larger its compressions, the larger its amplitude is and the more amplitude is and the more energy the wave carries.energy the wave carries.
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Frequency, fFrequency, f•The number of wavelengths that The number of wavelengths that
pass a fixed point each second.pass a fixed point each second. •The rate of vibrationThe rate of vibration•Find the frequency of a Find the frequency of a
transverse wave by counting the transverse wave by counting the number of crests or troughs that number of crests or troughs that pass by a point each second.pass by a point each second.
•Expressed in Expressed in HertzHertz (Hz). (Hz).
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Period, TPeriod, T•The amount of time it takes one The amount of time it takes one
wavelength to pass a point.wavelength to pass a point.•As the frequency of a wave As the frequency of a wave
increases, the period increases, the period decreases.decreases.
•Units of seconds, s.Units of seconds, s.
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Frequency & PeriodFrequency & Period
•The frequency, f, and period, The frequency, f, and period, T, are reciprocals of each T, are reciprocals of each other.other.
• Tf1
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Speed of a WaveSpeed of a Wave•The speed of a wave depends on The speed of a wave depends on
the medium it is traveling the medium it is traveling through. through.
•Sound travels faster in solids Sound travels faster in solids than gases.than gases.
•Light travels faster in air than Light travels faster in air than water.water.
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Calculating the Speed of a Calculating the Speed of a WaveWave•v=fv=f•Where:Where:•v is speed in m/sv is speed in m/s•f is frequency in Hzf is frequency in Hz• is wavelength in mis wavelength in m