Chapter 20. Traveling Waves - Physics & Astronomy

1 Chapter 20. Traveling WavesChapter 20. Traveling WavesYou may not realize it, but you are surrounded by Waves . The waviness of a water wave is readily apparent, from the ripples on a pond to ocean Waves large Copyright 2008 Pearson Education, Inc., publishing as Pearson pond to ocean Waves large enough to surf. It s less apparent that sound and light are also Goal:To learn thebasic properties of Traveling : The Wave Model One-Dimensional Waves Sinusoidal Waves Chapter 20. Traveling WavesChapter 20. Traveling WavesCopyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley.

2 Waves in Two and Three Dimensions Sound and Light Power, Intensity, and Decibels The Doppler EffectChapter 20. Reading QuizzesCopyright 2008 Pearson Education, Inc., publishing as Pearson 20. Reading QuizzesA graph showing wave displacement versus position at a specific instant of time is called aA. snapshot history 2008 Pearson Education, Inc., publishing as Pearson line composite graph showing wave displacement versus position at a specific instant of time is called aA. snapshot history 2008 Pearson Education, Inc., publishing as Pearson line composite graph showing wave displacement versus time at a specific point in space is called a A.

3 Snapshot history 2008 Pearson Education, Inc., publishing as Pearson line composite graph showing wave displacement versus time at a specific point in space is called a A. snapshot history 2008 Pearson Education, Inc., publishing as Pearson line composite wave front diagramshowsA. the wavelengths of a the crests of a how the wave looks as it moves toward 2008 Pearson Education, Inc., publishing as Pearson the forces acting on a string that s under Wave front diagrams were not discussed in this wave front diagramshowsA. the wavelengths of a the crests of a how the wave looks as it moves toward 2008 Pearson Education, Inc.

4 , publishing as Pearson the forces acting on a string that s under Wave front diagrams were not discussed in this Waves analyzed in this Chapter areA. string Waves . B. sound and light Waves . C. sound and water , sound, and light 2008 Pearson Education, Inc., publishing as Pearson , sound, and light string, water, sound, and light Waves analyzed in this Chapter areA. string Waves . B. sound and light Waves . C. sound and water , sound, and light 2008 Pearson Education, Inc., publishing as Pearson , sound, and light string, water, sound, and light 20.

5 Basic Content and ExamplesChapter 20. Basic Content and ExamplesCopyright 2008 Pearson Education, Inc., publishing as Pearson 20. Basic Content and ExamplesChapter 20. Basic Content and ExamplesTransverse and Longitudinal WavesCopyright 2008 Pearson Education, Inc., publishing as Pearson and Longitudinal WavesCopyright 2008 Pearson Education, Inc., publishing as Pearson SpeedThe speed of transverse Waves on a string stretched with tension TsisCopyright 2008 Pearson Education, Inc., publishing as Pearson is the string s mass-to-length ratio, also called the linear The speed of a wave pulseQUESTION:Copyright 2008 Pearson Education, Inc.

6 , publishing as Pearson The speed of a wave pulseCopyright 2008 Pearson Education, Inc., publishing as Pearson The speed of a wave pulseCopyright 2008 Pearson Education, Inc., publishing as Pearson The speed of a wave pulseCopyright 2008 Pearson Education, Inc., publishing as Pearson The speed of a wave pulseCopyright 2008 Pearson Education, Inc., publishing as Pearson Waves To understand Waves we must deal with functions of twovariables, position and time. A graph that shows the wave s displacement as a function of position at a single instant of time Copyright 2008 Pearson Education, Inc.

7 , publishing as Pearson function of position at a single instant of time is called a snapshot graph. For a wave on a string, a snapshot graph is literally a picture of the wave at this instant. A graph that shows the wave s displacement as a function of time at a single position in space is called a history graph. It tells the history of that particular point in the Finding a history graph from a snapshot graphQUESTION:Copyright 2008 Pearson Education, Inc., publishing as Pearson Finding a history graph from a snapshot graphCopyright 2008 Pearson Education, Inc.

8 , publishing as Pearson Finding a history graph from a snapshot graphCopyright 2008 Pearson Education, Inc., publishing as Pearson Finding a history graph from a snapshot graphCopyright 2008 Pearson Education, Inc., publishing as Pearson Finding a history graph from a snapshot graphCopyright 2008 Pearson Education, Inc., publishing as Pearson Waves A wave source that oscillates with simple harmonic motion (SHM) generates a sinusoidal wave. The frequencyfof the wave is the frequency of the oscillating source. The periodTis related to the wave frequency fbyCopyright 2008 Pearson Education, Inc.

9 , publishing as Pearson Addison-Wesley. The amplitudeAof the wave is the maximum value of the displacement. The crests of the wave have displacement Dcrest= Aand the troughs have displacement Dtrough= A. Sinusoidal WavesCopyright 2008 Pearson Education, Inc., publishing as Pearson Waves The distance spanned by one cycle of the motion is called the wavelength of the wave. Wavelength is measured in units of meters. During a time interval of exactly one period T, each crest of a sinusoidal wave travels forward a distance of exactly one wavelength .Copyright 2008 Pearson Education, Inc.

10 , publishing as Pearson one wavelength . Because speed is distance divided by time, the wave speedmust beor, in terms of frequencySinusoidal Waves The angular frequencyof a wave is The wave numberof a wave isCopyright 2008 Pearson Education, Inc., publishing as Pearson Addison-Wesley. The general equation for the displacement caused by a Traveling sinusoidal wave isThis wave travels at a speed v= in Two and Three Dimensions Suppose you were to take a photograph of ripples spreading on a pond. If you mark the location of the crests on the photo, these would be expanding concentric circles.