Chapter 11 WavesChapter 11 TopicsWaves and Energy TransportSlide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Transverse Waves on a StringSlide 12Slide 13Slide 14Periodic WavesSlide 16Slide 17Slide 18Slide 19Slide 20The Principle of SuperpositionSlide 22Reflection and RefractionSlide 24Slide 25Slide 26Slide 27InterferenceSlide 29Slide 30Slide 31Slide 32Slide 33Slide 34Slide 35Standing WavesSlide 37Slide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45SummarySlide 47Slide 48Chapter 11WavesMFMcGraw Ch-11b-Waves - Revised 4-3-10 2Chapter 11 Topics •Energy Transport by Waves•Longitudinal and Transverse Waves •Transverse Waves on Strings•Periodic Waves•Superposition•Reflection and Refraction of Waves•Interference and Diffraction•Standing Waves on a StringMFMcGraw Ch-11b-Waves - Revised 4-3-10 3Waves and Energy Transport•A wave is a disturbance that travels, in a medium, outward from its source. •Waves carry energy. •The energy is transported outward from the source to the destination.•The matter in the medium expieriences no net transport.MFMcGraw Ch-11b-Waves - Revised 4-3-10 4When a stone is dropped into a pond, the water is disturbed from its equilibrium positions as the wave passes; it returns to its equilibrium position after the wave has passed.The water moves up and down as the disturbance moves outward but is not transported by the wave.Waves and Energy TransportMFMcGraw Ch-11b-Waves - Revised 4-3-10 5A Simple Water WaveThe wave travels to the right. The individual water molecules move up and down locally but do not travel with the wave. A surfer CAN travel with the wave, at least for a while.Trough PeakMFMcGraw Ch-11b-Waves - Revised 4-3-10 63-D Spherical WaveEnergy spreads out, from a point source, uniformly over a 3 dimensional areaIntensity = Power/AreaUnits: Watts/m2MFMcGraw Ch-11b-Waves - Revised 4-3-10 7Intensity is a measure of the amount of energy/sec that passes through a square meter of area perpendicular to the wave’s direction of travel.22r4r4PowerPI Intensity has units of watts/m2 .This is an inverse square law. The intensity drops as the inverse square of the distance from the source. (Light sources appear dimmer the farther away from them you are.)Waves and Energy TransportMFMcGraw Ch-11b-Waves - Revised 4-3-10 8Example: At the location of the Earth’s upper atmosphere, the intensity of the Sun’s light is 1400 W/m2. What is the intensity of the Sun’s light at the orbit of the planet Mercury? 2essune 4 rPI2mssunm 4 rPIDivide one equation by the other (take a ratio):2em210112mses2essun2mssunem W/m920057.657.6m 1085.5m 1050.1r 4r 4IIrrPPIIWaves and Energy TransportMFMcGraw Ch-11b-Waves - Revised 4-3-10 9Longitudinal WaveAmplitude change parallel to propagation directionTransverse WaveAmplitude change perpendicular to propagation directionMFMcGraw Ch-11b-Waves - Revised 4-3-10 10The Excitation of a Transverse WaveThe speed with which the string is moved vertically is independent of the speed with the wave travels horizontally down the string.Boundary Condition:The end of the string is stationaryMFMcGraw Ch-11b-Waves - Revised 4-3-10 11Transverse Waves on a StringMAttach a wave driver hereLAttach a mass to a string to provide tension. The string is then shaken at one end with a frequency f.MFMcGraw Ch-11b-Waves - Revised 4-3-10 12A wave traveling on this string will have a speed ofFv where F is the force applied to the string (tension) and  is the mass/unit length of the string (linear mass density).Transverse Waves on a StringMFMcGraw Ch-11b-Waves - Revised 4-3-10 13Example (text problem 11.8): When the tension in a cord is 75.0 N, the wave speed is 140 m/s. What is the linear mass density of the cord?Fv The speed of a wave on a string is kg/m 108.3m/s 140N 0.75322vFSolving for the linear mass density:Transverse Waves on a StringMFMcGraw Ch-11b-Waves - Revised 4-3-10 14Speed of Sound in Various Materials F ForcevInertia  Bv YvIncreasing attractive force String Liquid SolidHigh mass Low MassMFMcGraw Ch-11b-Waves - Revised 4-3-10 15Periodic WavesA periodic wave repeats the same pattern over and over.•For periodic waves: v = f•v is the wave’s speed•f is the wave’s frequency is the wave’s wavelengthMFMcGraw Ch-11b-Waves - Revised 4-3-10 16A Simple Harmonic OscillatorIts motion, depicted as a function of time, is a wave.Apeak-peak = Ap-p = 2Apeak = 2Ap; Ap = Ap-p /2MFMcGraw Ch-11b-Waves - Revised 4-3-10 17The period T is measured by the amount of time it takes for a point on the wave to go through one complete cycle of oscillations. The frequency is then f = 1/T.Periodic WavesMFMcGraw Ch-11b-Waves - Revised 4-3-10 18The maximum displacement from equilibrium is amplitude (A) of a wave.One way to determine the wavelength is by measuring the distance between two consecutive crests.Periodic WavesMFMcGraw Ch-11b-Waves - Revised 4-3-10 19Example (text problem 11.13): What is the wavelength of a wave whose speed and period are 75.0 m/s and 5.00 ms, respectively?  m 3750s 10005m/s 0753...vT Solving for the wavelength:TfvPeriodic WavesMFMcGraw Ch-11b-Waves - Revised 4-3-10 20Wave PropertiesMFMcGraw Ch-11b-Waves - Revised 4-3-10 21The Principle of SuperpositionFor small amplitudes, waves will pass through each other and emerge unchanged.Superposition Principle: When two or more waves overlap, the net disturbance at any point is the sum of the individual disturbances due to each wave.MFMcGraw Ch-11b-Waves - Revised 4-3-10 22Two traveling wave pulses: left pulse travels right; right pulse travels left.MFMcGraw Ch-11b-Waves - Revised 4-3-10 23Reflection and Refraction At an abrupt boundary between two media, a reflection will occur. A portion of the incident wave will be reflected backward from the boundary.MFMcGraw Ch-11b-Waves - Revised 4-3-10 24When you have a wave that travels from a “low density” medium to a “high density” medium, the reflected wave pulse will be inverted. (180o phase shift.) The frequency of the reflected wave remains the same.The Reflected Wave & Phase ChangeMFMcGraw Ch-11b-Waves - Revised 4-3-10 25When a wave is incident on the boundary between two different media, a portion of the wave is reflected, and a portion will be transmitted into the