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Waves & Sound

Waves & Sound

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Waves & Sound

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  1. Waves & Sound

  2. Lesson 1 - Wave Intro

  3. Waves What is the definition of a wave with relation to energy?

  4. Characteristics of a Wave What is the Amplitude of a wave? What units is Amplitude measured in? What is the wavelength of a wave? What is the variable for wavelength? What is the unit for wavelength?

  5. Characteristics of a Wave On this wave, the wavelength and amplitude (in that order) are represented as segments A. BD and HC • BD and IC • CE and IC • CG and HC • None of these

  6. Characteristics of a Wave What is the definition of period of a wave? What is the variable for period? What is the unit for period? What is the definition of frequency of a wave? What is the variable for frequency? What is the unit for frequency? How is the frequency related to the period?

  7. Period vs Frequency If a spring oscillates up and down 8 times in 2 seconds, what is the period? • 0.25 s • 2 s • 4 s • 8 s • 16 s Follow-up: What is the frequency?

  8. Period vs Frequency If a pendulum oscillates back and forth 4 times in 12 seconds, what is the frequency? • 0.33 Hz • 3 Hz • 4 Hz • 12 Hz • 48 Hz Follow-up: What is the period?

  9. Speed of a Wave What is the equation that describes the speed of a wave?

  10. Speed of a Wave Waves in the ocean measure about 5m apart, and about 1.5m tall. They crash on the shore once every 2.5 seconds. What is the approximate speed of these ocean waves? • 0.6 m/s • 2 m/s • 2.6 m/s • 3.75 m/s • 12.5 m/s

  11. Speed of a Wave A sound wave with a wavelength 0.725m, a period of 5 × 10-4s, and a frequency of 2,000 Hz traveling through water can go 4.35 km in 3 seconds. What is the speed of the sound wave. • 3.625 × 10-4 m/s • 1.45 m/s • 0.24 m/s • 8700 m/s • None of these

  12. Types of Waves Describe a transverse wave.

  13. Types of Waves Describe a longitudinal wave.

  14. Animations of Types of Waves • http://einstein.byu.edu/~masong/HTMstuff/WaveTrans.html • http://www.gmi.edu/~drussell/Demos/waves/wavemotion.html

  15. Lesson 2 – Sound Waves & Interference

  16. Sound Waves Look in your textbook in Ch26 What type of wave is a sound wave, transverse, longitudinal, combination, or other? What is the source of any sound wave? Does a sound wave require a medium through which to travel?

  17. Sound Waves What is the process by which we convert sound waves into perceived audible sound?

  18. Sound Waves How fast do sound waves travel through air? (assume room temp, and at sea-level) _____________ m/s ___________ mph What happens to the speed of sound when it travels through a liquid or a solid?

  19. Sound Waves What characteristic of a sound wave determines the pitch or note of a sound? How does it change if there is a higher pitch heard (higher note)? What characteristic of a sound wave changes if there is a louder heard (higher note)? (think about it…you probably won’t find it in the reading).

  20. Interference Look at physicsclassroom.com for Interference What causes wave interference to occur? What meant by wave superposition?

  21. Constructive Interference When does constructive interference occur? How would you find the superposition of two waves experiencing constructive interference?

  22. Destructive Interference When does destructive interference occur? How would you find the superposition of two waves experiencing destructive interference?

  23. Beats When do beats occur? What is the equation for beat frequency? What would cause the beat frequency to decrease?

  24. Natural Frequency Look in your textbook on Pg 520 What is an object’s natural frequency? When do forced vibrations occur?

  25. Resonance When does resonance occur?

  26. Demonstration Bell in jar

  27. Demonstration Tuning forks (observing) (water, octave)

  28. Demonstration Microphone graphed on oscilloscope

  29. Demonstration Slinky in hall with constructive & destructive interference

  30. Superposition of Waves What is the resultant wave pattern formed when these two waves overlap? A. B. C. D. E. None of these

  31. Superposition of Waves What is the resultant wave pattern formed when these two waves overlap? A. B. C. D. E. None of these

  32. Demonstration Speaker in phase and out of phase

  33. Interference of Sound Waves Acoustic Engineering – designing concert halls http://www.acoustics.salford.ac.uk/feschools/waves/super2.htm

  34. Tuning Fork What happens to the pitch of the tuning fork when the mass is lowered? • Gets higher • Gets lower • Stays the same, no effect

  35. Beats http://www.acoustics.salford.ac.uk/feschools/waves/super3.htm#beats http://web.cortial.net/bibliohtml/p2onde_j.html

  36. Beats As the mass is lowered, what happens to the frequency at which the beats occur? • Increases • Decreases • Stays the same

  37. Demonstration Tuning fork on lab table – forced vibration and natural frequency

  38. Demonstration Tuning Forks on box - Resonance

  39. Resonance Tuning forks, wine goblet, swing-set, Tacoma Narrows bridge http://www.youtube.com/watch?v=JiM6AtNLXX4&feature=fvw http://www.youtube.com/watch?v=Jy8js2FmGiY http://www.youtube.com/watch?v=j-zczJXSxnw

  40. Lesson 3 – Standing Waves & Instruments

  41. Standing Waves Look at physicsclassroom.com What is a standing wave compared to a traveling wave?

  42. Nodes & Antinodes What is a node on a standing wave? What is an antinode on a standing wave? What causes a node versus what causes an antinode?

  43. Standing Wave Harmonics What is a harmonic? What is the 1st Harmonic Standing Wave pattern look like? What is the 2nd Harmonic Standing Wave pattern look like? What is the 3rd Harmonic Standing Wave pattern look like?

  44. Standing Wave Demos Transverse with Slinky. Is the amplitude of the antinode greater or equal to the amplitude of my hand shaking back and forth? Longitudinal with vertical spring on speaker oscillator.

  45. Spring Exploration Did a standing wave develop at any frequency you choose to shake the spring? What happened to the frequency at which you shook the spring to make a higher harmonic standing wave? Equation for harmonics:

  46. Equation for Standing Wave on a String Examples:

  47. Standing Wave on a String What is the speed of a wave on a 1.6m long bass guitar string if it plays a notes with a frequency of 75Hz at its fundamental frequency?

  48. Guitar String If I press my finger on a string, it makes the string shorter. What does that do to the frequency, and the perceived pitch (note)? • Frequency: increases Pitch: raises • Frequency: increases Pitch: lowers • Frequency: decreases Pitch: raises • Frequency: decreases Pitch: lowers • None of these

  49. Guitar String When I tighten a string, what does that do to the frequency, and why? • Increases, because the speed of the wave increases • Increases, because it is a higher harmonic • Increases because the length of the string increases • Decreases because the length of the string increases • None of these