2 WavesA propagation of energy through a medium without a transfer of the medium.
3 Two Types of Waves1) Transverse Wave – a wave where the disturbance of the medium is perpendicular to the direction of energy motion.Transverse Wave DiagramTransverse Diagram 1Transverse Water WaveTransverse Wave AnimationTransverse Wave Animation 1Longitudinal Wave (Compression Wave) – a wave where the disturbance of the medium is parallel to the direction of energy motion.Sound is a longitudinal wave.Longitudinal Wave 1Longitudinal Wave 2Longitudinal Wave 3Longitudinal Wave AnimationCompression – a region of high density in a longitudinal waveRarefaction – a region of low density in a longitudinal waveThe amplitude is represented by the amount of compression (density).Surface Wave – A combination of transverse and longitudinal waves.Surface Wave
4 Components of a Transverse Wave wavelength (λ)crestamplitudeEquilibriumPositiontroughCrest: the location of maximum displacement on a wave.Trough: the location of the lowest displacement on a wave.Equilibrium position: the undisturbed position of the mediumAmplitude: the displacement from the equilibrium position to crest or trough.The amplitude represents the energy in a wave.Wavelength (λ): the distance between the same two locations on adjacent waves.
5 Wave Pulse Periodic Wave A single disturbance in the medium Wave Pulse AnimationWave PulsePeriodic WaveA repetitious wave.Transverse Wave
6 Two categories of waves Matter Wave (Mechanical Wave) – a wave that needs a medium to travel throughExamples: Earthquake The Earthquake ShakeA vibrating guitar stringThe surface of water Water Surface WaveElectromagnetic Wave – a wave that does not need a medium to travel throughExample: Radio waves, TV waves, light, x-rays Electromagnetic Waves
7 Speed of a Wave v=λ / T v=fλ wavelength (λ) T =period: the amount of time for one wave to be created.f = frequency: the number of waves created in one second.Frequency is measured in Hertz (Hz) which has the fundamental unit of s-1 (1/s)T=1/fv=d/t = λ /Tv=λ / Tv=fλExample: What is the speed of the wave above if its created in 4.0 sand has a wavelength of 12.0 m?v=λ/T = 12.0 m / 4.0s = 3.0 m/s
8 Speed of a wave (cont.) v=fλ λ v=d/t f= #waves / time The above waves are created in 6.0 s and has a wavelength of 9.0 m. What is the speed of the waves?f=3 waves/6.0s =.50 Hzv=fλ=(.50 Hz)(9.0m)=4.5 m/s
9 Wave Properties Frequency: Increased Wavelength: Decreases In one medium:Speed: Unchanged as it travels through a medium. The wave speed is dependent only on the properties of the medium.Frequency: Increased Wavelength: DecreasesFrequency: Decreased Wavelength: Increases
10 A graphical explanation of why wavelength is dependent on speed: The speed of the vehicle are constant.A larger frequency of cars:A smaller frequency of cars:
11 Mathematical explanation of why wavelength varies with speed: Speed remains constant in a medium.vf=λfLarge frequency, short wavelengthv=λλSmall frequency, long wavelengthv=f
12 Wave Properties between Media Wave ReflectionIncident wavetransmitted wavereflected waveMedium 2Medium 1Incident wave: The original wave that approaches the boundary between two media.Reflected wave: The portion of the wave redirected back into the first medium.Transmitted wave: The portion of the original wave that the transferred into the newmedium.The more similar the properties between the two media the more of the wave that istransmitted.
13 Phase of the Reflected Wave phase – the position of a wave.inverted wave (180º phase shift) erect wave (0º phase shift)incident waveincident waveincident wavereflected wavereflected waveReflected wave is erectReflected wave is invertedIf the new medium is more dense than the previous medium, the reflected wavewill be inverted.If the new medium is less dense than the previous medium, the reflected wavewill be erect.
14 Wave InterferenceInterference- The interaction between two or more waves simultaneously occupying the same location.Principle of superposition – the algebraic sum of two or more waves.Constructive interference will occur in the following situation when the waves occupythe same position at the same time.BAThe principle of superposition showsthe resulting wave of both Interfering.Constructive interferenceA+BBAThe wave continue traveling in the samedirection unaffected by the wave interference.
15 the same position at the same time. Destructive interference will occur in the following situation when the waves occupythe same position at the same time.ABThe principle of superposition showsthe resulting wave of both Interfering.Destructive interferenceA+BAfter the interference the waves continue traveling In the same direction unaffected by the interference.ABTotal Destructive interference will occur when two waves with equal magnitude, butopposite directions interfere as show below.ABA+BThe waves continue travelingin the same direction unaffectedby the wave interference.AB
16 Wave Component Properties Traveling between Media Amplitude:DecreasesWavelength:ChangesSpeed:Frequency:ConstantEnd
18 Standing Waves Standing wave demonstration Standing Wave Diagram Fluctuating stationary waves formed by the interference of traveling waves of the same frequency,speed and amplitude moving in opposite directions.Standing wave demonstrationStanding Wave DiagramStanding Wave AnimationStanding Wave Animation 1Standing Wave Animation 2Standing Wave Animation 3
19 Wave Fronts wave front: a short hand notation of representing the crest of a wave.
20 Law of ReflectionThe angle of incidence is equal to the angle of reflection. (θi=θr)Incident waveBarrierθiθrNormal: a perpendicularto the surface of an object.θi=angle of incidenceθr=angle of reflectionReflected wave
21 RefractionThe change in direction of a wave when traveling from one medium to another.medium 2medium 1wave directionin medium 2wave directionin medium 1
22 DiffractionDiffraction: the bending and spreading of a wave that passes through an openingor around an obstacle.The smaller the opening compared the wavelength of the wave, the greater thediffraction.Diffraction
23 Sound Audible frequency range: 20 Hz to 20 kHz The vibration of air molecules in a medium perceivable by the human ear.Pitch – how the frequencies of sound is perceived.Audible frequency range: 20 Hz to 20 kHzInfrasonic region: Frequencies less than 20 HzUltrasonic region: Frequencies above 20 kHzThe ultrasonic region limit is 1 GHz.Sound in air is a longitudinal wave.Sound in a liquid or gas is primarily longitudinal, but contains a small fraction of atraverse wave component.
24 Speed of Sound The speed of sound in air at 0ºC is 331 m/s. The speed of sound increases as temperature increases.v=(331m/s +.6Tc) for environmental temperatures.v=331m/s(1+Tc/273m/s)1/2 for higher temperatures.Mach number: A multiple of the speed of soundExample: Mach 2 at 0ºC is 662 m/s.What is the speed of a jet traveling at Mach 3 at 0º?993 m/s
25 The Doppler EffectThe perceived frequency change of sound because of a wavelength change due to relative motion between a source and an observer.numerator: + source moving towards observer- source moving away from observerdenominator: - observer moving towards source+ observer moving away from sourcev = speed of sound at a given temperaturevo = speed of the observer of the soundvs = speed of the source of the sound
26 ResonanceA matched frequency between a source and an object which causes increased oscillation vibrations of the object.
27 BeatsFluctuations in intensity between two sound frequencies due constructive and destructive interference of the sound waves.fb=|f1-f2|fb:beat frequency