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WAVES

WAVES. disturbance caused by the movement of energy from a source through some medium (solid, liquid or gas). WAVES. The energy is moving at the speed of the wave, but NOT the water. WAVES. The parcel of water moves in a circular motion = orbit. Fig. 9-3, p. 201. WAVES.

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WAVES

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  1. WAVES • disturbance caused by the movement of energy from a source through some medium (solid, liquid or gas).

  2. WAVES • The energy is moving at the speed of the wave, but NOT the water

  3. WAVES • The parcel of water moves in a circular motion = orbit

  4. Fig. 9-3, p. 201

  5. WAVES • Because the wave form moves forward these are called progressive waves

  6. Fig. 9-2, p. 201

  7. Orbits • The diameter of the orbits diminishes rapidly with depth • Wave motion in deep water is negligible past ½ the wavelength

  8. Stoke’s Drift or Mass Transport • Small net movement of water in the direction of the wave

  9. Classifying Waves • disturbing force = the energy that cause waves to form • restoring force = the dominant force trying to return surface water to flatness • wavelength

  10. Table 9-1, p. 202

  11. Figure 8.9

  12. Deep vs Shallow Water waves • The orbits of water molecules in a wave are circular only when the wave is in deep water • A wave cannot “feel” the bottom if it is in water deeper than ½ its wavelength • = a deep water wave

  13. Figure 8.7a: Deep Water Wave

  14. Transitional waves = travel through water deeper than 1/20 their wavelength and shallower than ½ its wavelength Figure 8.7b

  15. Figure 8.7c Shallow water waves = moving in water shallower than 1/20 it wavelength Water at the bottom moves back and forth

  16. Deep vs Shallow Water Waves • ONLY WIND WAVES CAN BE DEEP WATER WAVES

  17. How waves break at shore... • A deep water waves feels bottom and becomes a transitional wave then a shallow water wave • orbits become elliptical • crests become peaked so wave height increases • Waves in front slow down so wave length decrease

  18. How waves break at shore... • The wave becomes too high for its wavelength and the wave breaks • Wave steepness is waveheight/wavelength • When H/L = 1/7, the wave breaks • The surf zone is the region between the breaking waves and the shore.

  19. How large do wind waves get? • Depends on • wind strength • wind duration • fetch (distance over which wind blows) • Waves spread out (dispersion) based on size (large waves move faster) • Capillary waves … wind waves…fully developed seas…swell

  20. Figure 8.10

  21. Fig. 9-9, p. 207

  22. Highest wave: 1933 – in Pacific during a strong storm: strong wind in one direction for days…112ft (34 m) Fig. 8.12

  23. INTERFERENCE • Destructive interference = cancellation effects of subtraction • When a wave crest and another wave’s trough coincide

  24. INTERFERENCE • Constructive interference = addition effects that form large crests and deep troughs • When crests coincide

  25. Figure 8.15

  26. Figure 8.16

  27. Fig. 9-13 (a-b), p. 209

  28. Constructive Interference can cause “Rogue Waves” Fig. 9-13c, p. 209

  29. A 20 m (66 ft) wave in Hawaii Fig. 9-16, p. 211

  30. Wave Refraction • When waves do not approach parallel to shore… • The wave line will bend to become more parallel to shore

  31. Figure 8.19a

  32. Figure 8.19b

  33. Figure 8.19c

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