Lecture Notes: Wave Dynamics and Refraction

Key Concepts

• Wave Period and Wind Influence

  • Increase in wave period is associated with increased wind speed.
  • Key factors for creating large waves: wind speed, duration, and fetch (distance wind blows in one direction).
  • Example: Wave period increases from 8 to 20 seconds; wavelength increases from 100 meters to 625 meters.
  • Wave speed also increases in deep water where waves don't interact with the sea floor.

• Wave Base and Orbital Motion

  • In deep water, the wave base is unaffected by the sea floor.
  • Example: A wave with a 100-meter wavelength has a 50-meter wave base (half the wavelength).

Wave Refraction

• Understanding Wave Crests and Rays

  • Wave crests represent the tops of waves, while wave rays indicate wave travel direction.
  • Refraction occurs as waves bend towards the coast, influenced by the transition from deep to shallow water.
  • Real-life example: Waves wrapping around an island and colliding, observed on a boat trip from West Timor to Bali.

• Drawing Wave Crests and Rays

  • Wave rays are drawn at 90 degrees to wave crests, indicating wave bending.
  • In shallow water, one side of a wave slows, while the other speeds up, resulting in bending.
  • Techniques for drawing include starting near the coast and extending outward.

Observations and Real-Life Examples

• Live Camera Observation

  • Example: Waves observed at Swami's reef showing refraction as they change direction upon hitting shallower parts.

• Wave Refraction in Small Waves

  • Even tiny waves show refraction patterns, useful for understanding deeper and shallower areas in a body of water.
  • Visualization of squirrel surfing on refracted tiny waves as a humorous example.

• Refraction in Various Locations

  • Case Study: Refraction observed in Morocco where waves change direction significantly around a headland.
  • Importance for surfers: Clean and optimal wave conditions arise from significant refraction.

Conclusion

• Importance of Refraction

  • Refraction is a critical concept in understanding wave behavior and optimizing conditions for surfing.
  • Visual examples help grasp the bending nature of wave refraction.

• Next Steps

  • Practice drawing wave crests and rays on worksheets.
  • Analyze real-world wave refraction through local webcams and apply concepts learned.