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# Waves: Take 2

Waves: Take 2. Mr. Davis. p. 344 3,5,20,32,33,38,40,43,45. Review : Key characteristics of waves. All of these terms are required for the Regents.

## Waves: Take 2

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1. Waves: Take 2 Mr. Davis

2. p. 3443,5,20,32,33,38,40,43,45

3. Review: Key characteristics of waves All of these terms are required for the Regents Amplitude: The height of the wave from node to antinode (transverse waves), or the pressure in a compressive wave. Measured in units describing the wave Wavelength: The distance traversed by a full cycle of the wave Node: The “zero point” of the wave Antinode: The extreme point of the wave (max or min amplitude) Period: The time between successive waves Frequency: The rate of occurrence of the wave (in Hertz or cycles / second) The frequency f = 1/T where T is the period. Period (if axis is time)

4. How does a string make music? • What does a string look like when vibrating? How do I measure Amplitude Wavelength Frequency Period For each of these?

5. Videos: Superposition and wavelength as a function of gas composition http://www.acs.psu.edu/drussell/Demos/superposition/superposition.html http://www.wired.com/wiredscience/2008/09/top-10-amazing/

6. Standing waves • Two similar periodic waves traveling in opposite directions form a standing wave.

7. V = nf/2L L = l/2

8. What happens when two waves collide?

9. What happens when two waves collide? What happens when many people in the same room talk? What happens when an orchestra plays? What happens when waves interact in the ocean? (The Perfect Storm) What happens when two billiard balls collide? What happens under the Cone of Silence?

10. What happens when two waves collide? They can cancel: Superposition (This is really addition of components of inverse sign)

11. What happens when two waves collide? They can add: Superposition

12. What happens when two waves collide? They pass through each other without affecting each other and keep on going

13. What happens when two waves collide? They pass through each other without changing and keep on going. (Have you ever crossed the beams of two flashlights to see what would happen?)

14. What happens when two waves collide? They pass through each other without changing and keep on going. (Have you ever crossed the beams of two flashlights to see what would happen?)

15. http://bestphysicsvideos.blogspot.com/2011/07/mit-physics-demo-wave-superposition.htmlhttp://bestphysicsvideos.blogspot.com/2011/07/mit-physics-demo-wave-superposition.html MIT Demonstration of Bell Labs Wave machine

16. Beat Frequency Two waves of similar frequency Beat frequency is the difference between them Fundamental Frequency and Harmonics

17. Speed of Waves Waves have a speed! Dependent on • Medium • Temperature • Pressure • Frequency (wavelength) What about light? • Medium • Wavelength (frequency) • (temperature) • (pressure)

18. Speed of Waves • The relationship between wave speed, wavelength, and frequency is simple • For a given temperature, pressure, material, etc. • v = fl, where v is the speed, f is the frequency, and lambda is the wavelength. What is v for sound? What is v for light? What is v for a Slinky?

19. Speed of Waves http://www.pbs.org/wgbh/nova/earth/japan-killer-quake.html

20. Affects on sound waves • Vibration (tension) • Length • Resonance • Affects of sound waves • Shatter glass! • Transmit energy!