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Sine Curve

Sine Curve. Pictorial representation of a wave. Mechanical Waves. Requires a medium Cannot travel through empty space (in a vacuum) Ex. Water waves, sound. Electromagnetic Waves. Do NOT require a medium - can move through empty space (a vacuum)

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Sine Curve

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  1. Sine Curve • Pictorial representation of a wave

  2. Mechanical Waves • Requires a medium • Cannot travel through empty space (in a vacuum) • Ex. Water waves, sound

  3. Electromagnetic Waves • Do NOT require a medium - can move through empty space (a vacuum) • Ex. Radio waves, light waves, microwaves, x-rays

  4. WAVES • Transfer energy not matter from one place to another • Disturbance that moves through space or through a medium (material)

  5. Particles vibrate perpendicular to the wave motion Transverse waves can be polarized string musical instruments ripples on water electromagnetic waves e.g. Light waves, x-rays, radio waves TRANSVERSE WAVES

  6. Picture of a Transverse Wave Crest l Wavelength A A - Amplitude Trough

  7. Transverse Wave • http://dev.physicslab.org/Document.aspx?doctype=3&filename=WavesSound_IntroductionWaves.xml

  8. Longitudinal Wave • Compression-(similar to crests) – particles close together (high density) • Rarefactions (similar to troughs)- particles spread out or rarefied (low density)

  9. Sound • Travels as a longitudinal wave • sounds audible to humans range from 20 - 20,000 Hz • as f increases, pitch rises

  10. LONGITUDINAL WAVES Particles vibrate parallel to the motion of the waves Ex: Sound Waves • http://dev.physicslab.org/Document.aspx?doctype=3&filename=WavesSound_IntroductionWaves.xml

  11. SOUND FREQUENCY • Determines pitch • frequency and pitch are directly related • 20-20,000 Hz are audible to avg. person • < 20 Hz are infrasonic • > 20,000 Hz are ultrasonic

  12. What is the Mosquito Ring tone? • High pitched ring tone that most adults cannot hear • “teen buzz” • originally designed as a repellant • Mosquito ringtone is 17 kHz (that’s 17,000 Hz for those of you who forgot what a kilo is) • The highest note on a piano is only 4 kHz

  13. Hearing Range by Age Hearing Range kHz 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 2-16 kHz 2-14 kHz 2-12 kHz 2-11 kHz 18-21 yrs 30-39 yrs 40-49yrs 50-59 yrs

  14. Frequencies • http://www.opti.dyndns.org/~dng/SOUND/ReferenceSound/refsound.html • http://www.freemosquitoringtone.org/ Ringtones

  15. DOG IN WATER Dog swims to the right Dog treads water (no velocity) Dog swims at same speed as water waves he is creating

  16. Doppler Effect • A change in frequency due to a change in motion of either the vibration source or the observer

  17. Objects in motion compress the light waves in front of them making them appear more blue (blue shift), the light waves behind are stretched out and appear more red (red shift). http://cse.ssl.berkeley.edu/bmendez/ay10/2002/notes/lec8.html

  18. Reflection • Turning back of a wave at the boundary of a new medium • ex. Light off a mirror; sound echo

  19. Tacoma Narrows Bridge • Why did the Tacoma Narrows Bridge fall? • Video of bridge: http://www.archive.org/stream/SF121/SF121_256kb.mp4

  20. Tacoma Narrows Bridge • Collapsed Nov 7, 1940 • The failure of the bridge occurred when a never-before-seen twisting mode occurred. This is called a torsional mode whereby when the left side of the roadway went down, the right side would rise, and vice-versa, with the centerline of the road remaining still.

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