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Lecture series for Conceptual Physics, 8 th Ed.

“A wiggle in time.” p324. Sound needs a medium. Light does not need a medium. Lecture series for Conceptual Physics, 8 th Ed. Vibration of a Pendulum p325. T p =. 2 . L/g. Depends on length of string and gravity. Fig 18.1 In all cases, the motions are independent of mass.

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Lecture series for Conceptual Physics, 8 th Ed.

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  1. “A wiggle in time.” p324 Sound needs a medium. Light does not need a medium. Lecture series for Conceptual Physics, 8th Ed.

  2. Vibration of a Pendulum p325 Tp = 2 L/g Depends on length of string and gravity. Fig 18.1 In all cases, the motions are independent of mass. To and fro motion is called- Note: Sliding not rolling. Simple Harmonic Motion Pendulum dribbling sand makes a sine wave.

  3. Crest Trough The mass bobbing up and down on a spring exhibits simple harmonic motion. Frequency is the number of cycles per second. (Hz) Period is the number of seconds per cycle. (Tp) 1 Frequency = Period

  4. Waaavvee Moottionnn p328 Energy is transferred from source to receiver. Light and water waves: molecules of medium shake back and forth along wave path. These are transverse waves. p 329

  5. Wave Speed p328 Wave speed = wavelength x frequency v =  f Longitudinal Waves p330 Longitudinal (SOUND waves). Transverse

  6. Interference p331 Destructive Constructive Recall noise canceling headsets.

  7. Standing Waves p332 Figure 18.13 The incident and reflected waves interfere to produce a standing wave.

  8. Doppler Effect p333 Stationary bug standing on water produces concentric waves. When the bug moves to the right, it makes new circles. Each circle starts where the bug stepped. Longer wavelengths. Shorter wavelengths

  9. Bow Waves p335 Now, bug is going faster than wave speed. It’s stepping ahead of one wave to make the next. Fig 18-18 Wave pattern made by a bug swimming at wave speed.

  10. Shock Waves p336 The overlapping waves produce a sharp pressure increase. The shock wave, sonic boom, follows the plane.

  11. Sounds Waves The tuning fork is the wiggle in time. The sound waves move to the right. The molecules move to the right and then back to the left, returning to their original spot. The energy of the sound travels forward at the speed of sound, but each air molecule only oscillates back and forth along the direction that the wave is going. This type of motion is called LONGITUDINAL

  12. Refraction of Sound p346 Refraction mean bending. Sound travels faster in warm air than in cold air. The faster moving portion of the wave “goes ahead.” The wave changes direction as a portion of it goes ahead.

  13. Resonance p349

  14. Interference p350

  15. More interference fig 19-15 Constructive interference Destructive interference What you hear here. Beats p353 f=262Hz f=264Hz f=266Hz The “wah…wah…wah” sound, the beats, has a frequency of 4Hz. Sounds like the end.

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