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Wave Review

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  1. Wave Review

  2. If a vibrational disturbance occurs, energy travels/propagates out in all directions from the vibrational source. 1 disturbance = pulse

  3. Oscillators generate continuous waves • Many pulses = continuous wave.

  4. Traveling waves (as opposed to standing waves) transfer energy! Matter is not transferred by waves Give example of how we know E gets transferred.

  5. Wave Vocabulary • Points in Phase. • 1 cycle passes in time = 1 period • f = cycles passing per sec Hz • Medium – matl wave travels through. l crests Equilibrium

  6. 1. The wave below shows a “snapshot” that lasted 4.0 seconds. What is the frequency of the wave? 4.0 seconds 2 cycles/4 s = 0.5 Hz

  7. Transverse Waves • Earthquake S waves, EM waves.

  8. Longitudinal/CompressionalParticles compressed and expanded parallel to energy propagation. • Compressions – high P, density • Rarefactions- low P, density. • Sound.

  9. All points on a wave that are inphase comprise a wave front.

  10. Rays – a ray is an arrow sketched through the wave fronts (perpendicular) to show direction of wave propagation.

  11. Wave Speed • Speed/Velocity = d/t • If a crest (or any point on a wave) moves 20m in 5 sec, • v = 20m/5s = 4 m/s. • Waves of the same type travel through homogenous materials at same speed regardless of frequency of wavelength.

  12. Relationship of wave speed to wavelength(l) and frequency(f).v = d/t but for waves d = 1l occurs in time T (1period)so v = l/Tsince freq f =1/Tv =lf

  13. 2. A machine gun fires 10 rounds/sec at 300 m/s. a. What is the distance between the bullets? b. What would happen to the distance if the firing rate were increased. • f = 10 Hz. • v = 300 m/s. • l = ? • v = fl. • l = 300 m/s / 10 s-1. • l = 30 m.

  14. Wave Speed v = lf. Depends on medium Fixed by source oscillation Depends on the others.

  15. What can happen when wave pulses or continuous waves interact? • Transmission • Superposition & Interference

  16. What happens when they pass?

  17. Superposition – combining & addition of waves.

  18. Wave Superposition/Interference Destructive Constructive

  19. Boundary Behavior • Transmission (partial or not at all), • Reflection (partial or total) • Refraction – transmission with velocity change. • Diffraction – bending around boundary.

  20. Wave hits rigid boundary: • Reflection – pulse inverts. • It comes back totally opposite.

  21. Pulse hits soft boundary?

  22. Law of reflection

  23. Refraction – D speed and bending upon entering new material. The frequency is fixed by source. Constant speed until new material.

  24. Wavefronts entering new material

  25. Diffraction – curvature through small openings (apertures) or around obstacles.

  26. Curvature vs. Opening width

  27. Diffraction around obstacle.

  28. Never a frequency change unless the vibration rate of source changes. Or --

  29. Object & observer are in relative motion.

  30. Types of Waves • Mechanical • Non-mechanical • Medium • No medium

  31. Compressional/ pressure/ longitudinal • Always mechanical. Why? Examples?

  32. Transverse Examples?

  33. Polarization Transverse Waves

  34. Deduce that for waves Wave speed • v = lf.

  35. v = d t but for waves d = 1l occurs in time T v = l/Tsince freq f =1/Tv =lf

  36. d – time graph 1 point in oscillatory motion See hamper transverse.

  37. Displ – position graph shows the displacement of every point on wave at a given time. Need to see equilibrium position. See hamper longitudinal pg 91.

  38. IB Set IB Wave Prac 1 • Read hamper 4.4

  39. Frequency and Amplitude Physical Properties

  40. For light increased amplitude increases brightness.

  41. For sound: increased amplitude increases volume.

  42. Wave frequency (f, l) Wave type for EM waves. Color for light. Sound = f pitch

  43. Doppler Effect Objects in relative motion: toward each other – frequency increases (l decreases). away – frequency decreases (l increases).

  44. Doppler • Red/Blue Shift galaxies and stars.

  45. Sound

  46. Increasing velocity Sound velocity solid liquid gas In gas hot faster. cold slower.

  47. Resonance & Sympathetic Vibration

  48. All objects have a natural frequency of vibration. Resonance- the inducing of vibrations of a natural rate by a vibrating source having the same frequency “sympathetic vibrations” System resonance – amplitude will increase.

  49. Push at natural frequency, amplitude increases

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