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# Speakers

Speakers . When two waves meet their amplitudes add. Constructive interference—the two waves add to make a wave of greater amplitude. Destructive interference—the two waves are opposite in amplitude and cancel each other out. Connecting Speakers In-Phase. Out-of-Phase Speakers.

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## Speakers

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### Presentation Transcript

1. Speakers

2. When two waves meet their amplitudes add. Constructive interference—the two waves add to make a wave of greater amplitude. Destructive interference—the two waves are opposite in amplitude and cancel each other out.

3. Connecting Speakers In-Phase

4. Out-of-Phase Speakers Active sound cancellation

5. In-Phase, Different Distance

7. What happens when a pulse hits the end and turns around? Does it return on the same side of the rope or does it invert? Reflection

8. Standing Waves • Two sine waves in different directions • Reflections • Slinky • Periodic laser potentials

9. In the standing wave shown, what is its wavelength? • In the standing wave shown, what is the amplitude? • the points which oscillate with the most amplitude are called antinodes 1 meter 10 cm

10. What is the wavelength of the wave which is generating the standing wave shown below? (a) L/3 (b) 2L/3 (c) L 123 Q8-3

11. LUKE 16:1-13 PARABLE OF THE UNJUST STEWARD

12. Resonance, Harmonics

13. Jigsaw Standing Wave Demo

14. Consider a 3-loop standing wave on an elastic cord. If I increase the tension in the cord, the velocity of the waves in the cord will (a) increase, (b) decrease, or (c) remain the same. J15-3

15. If I unhook and pull on the belt, I get • more loops • fewer loops • does not change the number of loops

16. The sound you hear from a violin is produced by . . . • The string —determines the pitch (frequency) • The violin body —couples sound to the air 3. The bow —provides the energy—driver

17. ResonanceWhen you push a Swing does it make a difference when you push? Tacoma Narrows Bridge http://www.youtube.com/watch?v=xox9BVSu7Ok

18. Violin • The fundamental frequency or 1st harmonic (the lowest frequency for that length) determines the ________ you hear. • The 2nd harmonic frequency is twice the frequency of the first harmonic – a violinist can remove the fundamental by lightly touching the string at the half way point and you hear the 2nd harmonic. pitch

19. For a finite string (a violin string, for example), to change the fundamental frequency you can change . . . • the length of the string. • the mass per unit length of the string. • the tension in the string.

20. You hear a violinist playing a series of notes by moving their fingers up the fingerboard to effectively reduce the length of the string. As she does this, the notes you hear . . . • become higher in pitch • become higher in pitch • stays the same pitch

21. You hear a violinist playing a series of notes by moving their fingers up the fingerboard to effectively reduce the length of the string. As she does this, the wave speed . . . • Decreases • Increases • Stays the same

22. A string fastened at both ends has a length of 1.0 m. Two possible wavelengths for standing waves are • 4 m and 2 m • 2 m and .5 m • 3 m and .5 m • 4 m and 1 m • 3 m and 2 m