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Introduction Sound Waves outline Slide 1 Introduction slide Slide 2 Parts of a wave The wave shown is transverse but the amplitude wavelength crests and troughs apply to compressional longitudinal waves also I have a word bank on top because many students have seen this before so I make them tell me where the labels go Discuss how to measure one complete wavelength peak to peak trough to trough wherever the wave repeats one cycle Slide 3 Compressional waves vs transverse What are the differences and similarities They have the same attributes from the previous slide They are different in the direction that the amplitude vibrates perpendicular to or parallel to the direction of the moving wave What are examples of each type of wave Light is a transverse wave and sound creates compressional waves Slide 4 Frequency the number of waves passing a point in a given amount of time Demonstration Click on the waveform to see it travel to the right Have a volunteer student measure with a stopwatch as the rest of the class counts 5 complete waves go by Calculate the frequency about 1 Hz Slide 5 Students are often confused by frequency and the unit of Hertz so I use this slide to show that Hertz can measure waves per second bears per second or anything happening regularly in time Answer appears after students try to answer the question Slide 6 Using the ideas of wavelength and frequency to find the speed of a wave Explain to students that if 3 waves pass a point in one second and each wave is 2 meters long then 6 meters will pass that point Again answer appears after students try to answer Slide 7 Sound waves travel at 343 m s under normal conditions but this value can change with humidity elevation etc The key concepts are that a sound must travel through a medium like the air and b the speed of a sound wave depends on how closely the material is packed together Slide 8 To re enforce the same idea we can see a column of air where something has caused a vibration at the left end

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