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Wave Motion

Wave Motion. Waves. A vibration that repeats regularly in space and time Transmitted from one place to another w/out actually transporting matter A transmission of Energy Require a medium (substance to travel through) Ex. Water waves, sound, wave in string/spring.

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Wave Motion

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  1. Wave Motion

  2. Waves • A vibration that repeats regularly in space and time • Transmitted from one place to another w/out actually transporting matter • A transmission of Energy • Require a medium (substance to travel through) • Ex. Water waves, sound, wave in string/spring

  3. Kanagawa Oki NamiUra - “The Great Wave off of Kanagua” - by HOKUSai

  4. Describing a Wave • Wavelength – (λ) – distance between identical parts of a wave. Length of wave • Amplitude (A)– height of a wave • Period (T) - time for one full wave to pass • Frequency (f) – cycles per second … how many full waves pass by per second

  5. Frequency & period • Frequency = 1/ Period • Period = 1 / Frequency • Reciprocals of each other…. • Waves per time (frequency) • Time per wave (Period)

  6. Simple Harmonic motion • Any regularly repeating vibration • Pendulum • Spring • Vibrations caused in buildings by wind • Steps of a person walking • Rules for waves can be used for anything that fits in this category

  7. Wave Motion • Transfers energy not matter • If stone dropped in water, the disturbance moves not the water

  8. Wave sPeed • Wave speed depends on the medium • The more rigid the medium the faster sound will travel through it • Wave speed = frequency X wavelength • v = f λ

  9. Transverse Waves • Medium vibrates in a directions perpendicular to the direction of the wave

  10. Longitudinal Waves • Medium vibrates in the same direction that the wave moves

  11. INterference • Constructive Interference • Waves can interfere w/ each other so that they add together to produce a larger wave • Destructive Interference • Waves can interfere w/ each other so that they subtract each other and cancel out • Demos

  12. Out of phase • Destructive interference • In phase • Constructive interference

  13. Diffraction • When waves collide w/ a barrier they have a tendency to wrap around the barrier • Break walls at the beach • This is why we can hear a person talking even if they are around the corner

  14. Diffraction

  15. Energy of Waves- Tsunamis • Tsunamis are large waves generated by a large earthquake or massive landslide • Travel at hundreds of miles per hour, have low amplitudes out at sea, but can become very high when approaching shore

  16. http://www.funkybiology.com/Destructive_Force_of_Tsunami_Waves_mov.movhttp://www.funkybiology.com/Destructive_Force_of_Tsunami_Waves_mov.mov • http://www.youtube.com/watch?v=dJBS94GVyuo • http://www.youtube.com/watch?v=BAuWa77vYDU • http://www.youtube.com/watch?v=z-t5qe_VSEA • http://www.youtube.com/watch?v=wHtvA-lIksU • http://www.youtube.com/watch?v=sBkMLYUyUZg&safe=active (new)

  17. Sound • Longitudinal wave • Sound travels as a region of compressed air • The areas in between compressed regions are called “rarefactions” • Speed of sound is about 340 m/s in air • Like any wave the speed depends on the medium

  18. Sound • Frequency of a sound wave affects the “pitch” or how we hear a sound • Higher frequency, higher the pitch • Humans can typically hear pitches ranging from 20 Hz (infrasonic) to 20,000 Hz (ultrasonic), but that range diminishes as you age… typically at the high end • Loudness of a sound is affected only by amplitude

  19. http://www.cbu.edu/~jvarrian/applets/doppler1/doppler.htm • http://www.youtube.com/watch?v=AXhRmv1mrs4&safe=active • Hearing test • http://en.wikipedia.org/wiki/52-Hertz_whale • lonely whale • http://www.youtube.com/watch?v=h5l4Rt4Ol7M&safe=active • Hearing test

  20. Doppler Effect • Waves From an object that is approaching have short wavelength, which means they have a higher freq. And a higher pitch • waves coming from an object that is moving away from you have a longer wavelength and therefore a lower freq, and lower pitch • Cars approaching and leaving

  21. Bow shock/sonic Boom • Sometimes the source of a wave can travel faster than the waves it is creating • http://www.youtube.com/watch?v=6o0zmafxTmE&safe=active • Can be easily seen with a speed boat • http://www.youtube.com/watch?v=2Sv4o4Kktm4&safe=active • Sonic boom created when a object or plane breaks through the sound barrier

  22. Standing waves • Stationary wave caused by interference between a wave and its reflection • Two waves of equal amplitude and wavelength pass through each other in opposite directions. • Nodes – stationary points • Where waves our “out of phase” --- crest lined up with trough • Antinodes- points of largest amplitude • Where waves are “in phase” - crest lined up with crest • Standing Wave in Water • Standing wave demo • Standing waves created by speaker • Swimming pool • When an object is forced into vibrating at one of its natural frequencies, it vibrates in a manner such that a standing wave is formed within the object.

  23. Tacoma Narrows Bridge • http://www.youtube.com/watch?v=3mclp9QmCGs

  24. Resonance • When an object vibrates at its natural frequency, a dramatic increase in amplitude occurs • Resonance happens when a standing wave is created • Break Glass w/ voice? • Mythbusters

  25. Beats • Two tones of slightly different frequency are sounded together. This produces a fluctuation in the loudness of combined sounds. • adfs • Amount of beats per second is equal to the difference in frequencies. • Two tuning forks…. One 340 Hz another 310 Hz are sounded together. Beats will occur at a frequency of 30 Hz

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