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Physical Science CHAPTER 23

Physical Science CHAPTER 23. Waves. Waves transmit energy!!!. Mechanical Vs. Electromagnetic Waves Waves. Mechanical Waves Need medium (gas, liquid, solid) Examples: Sound, water waves.

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Physical Science CHAPTER 23

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  1. Physical ScienceCHAPTER23 Waves

  2. Waves transmit energy!!! Mechanical Vs. Electromagnetic Waves Waves

  3. Mechanical WavesNeed medium(gas, liquid, solid)Examples: Sound, water waves

  4. Electromagnetic WavesNo medium needed.Example: Visible Light (ROYGBIV), Ultraviolet, Infrared,Microwaves, etc…

  5. http://www.lbl.gov/MicroWorlds/ALSTool/EMSpec/EMSpec2.html

  6. 3 main characteristics of all Waves1. Amplitude(high amplitude means high energy)2. Wavelength (Unit: meters)3. FrequencyUnits: cycles/sec Waves/sec 1/s Hertz (Hz)

  7. Frequency Example Problem • A boy standing on a dock counts 20 waves • pass by in 5 seconds. What is the frequency • of the waves? f = #waves / time 20 waves / 5 seconds = 4 Hz

  8. Frequency Example Problem #2 • If the frequency of the waves is increased • to 8 Hz, how many waves will pass by the • boy in 2 seconds? f = #waves / time 8 Hz = #waves / 2 seconds 8 Hz x 2 seconds = 16 waves

  9. MECHANICAL WAVES (2 TYPES) TRANSVERSE WAVES LONGITUDINAL WAVES

  10. SURFACE WAVES http://www.gmi.edu/~drussell/Demos/waves/wavemotion.html

  11. TRANSVERSE WAVE

  12. LONGITUDINAL WAVE

  13. SPEED OF WAVESspeed = frequency x wavelength v = f x λ Example #1 A wave on a lake is traveling with a velocity of 8 m/s. the frequency is 2 Hz. What is the wavelength of this wave? 8 m/s = 2 Hz xλ λ = 4 m

  14. The Type Of Medium Determinesthe Speed of The WAVE!! Higher Density = Slower Speed of Wave Higher Elasticity = Faster Speed of Wave

  15. THE 4 BASIC WAVE INTERACTIONS ARE:1.   REFLECTION2.   REFRACTION3.   DIFFRACTION4.   INTERFERENCE

  16. 1. REFLECTIONBouncing back of waves upon reaching another surface.

  17. THE LAW OF REFLECTIONSTATES THAT THE ANGLE OF INCIDENCE IS EQUAL TO THE ANGLE OF REFLECTION.

  18. 2. REFRACTIONBending of waves due to a change in speed.

  19. 3. DIFFRACTIONBending of waves around the edge of an obstacle.

  20. 4. INTERFERENCE1.   CONSTRUCTIVE INTERFERENCEWhen waves combine and produce a wave that is greater than either of the waves alone.

  21. 2.   DESTRUCTIVE INTERFERENCEWhen waves combine and produce a wave that is less than either wave alone.

  22. Applet Interference by 3 wavessimultaneously. http://www.chipr.sunysb.edu/eserc/ProjectJava/WaveInteractionApplet/ Another wave website to look at: http://www.howe.k12.ok.us/~jimaskew/pwave.htm

  23. STANDING WAVESRESONANT FREQUENCY(or natural frequency)The frequency at which a standing wave occurs.

  24. RESONANCEThe ability of an object to vibrate by absorbing energy of its own natural frequency.Video clip of the Tacoma Narrows Bridge November 1940http://www.gmi.edu/~drussell/Demos.html

  25. NODESStationary points of a standing wave.ANTINODESLoops of a standing wave where maximum oscillation of the medium occurs.

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