Lecture on Wave Refraction

Introduction to Wave Refraction

• Wave refraction is a complex concept involving the bending of waves as they transition from deep to shallow water.
• Deep water waves travel at their original speed, but as they approach shallow water (near the shore), they slow down and bend.

Deep Water to Shallow Water Transition

• Waves seem to move straight to shore due to refraction, appearing to come from a westerly direction particularly on California's coast.
• Originating waves usually come from storms in the north or south Pacific or hurricanes.

Mechanics of Wave Refraction

• Deep water waves start feeling the ocean bottom, slowing down as they become shallow water waves.
• Refraction causes waves to bend towards shallow water, making them appear to come directly towards the shore.

Examples and Visuals

• Videos and animations can show how waves bend and wrap around coastlines due to varying depths.
• Waves near headlands bend more noticeably, creating specific surfing conditions.

Impact on Surfing

• Refraction creates famous surfing breaks, particularly in southern California spots like Rincon Point and Jaws in Maui.
• Waves change direction by up to 90 degrees due to extreme refraction, creating unique surfing waves like right breaks or A-frames.

Refraction Diagrams

• In labs, students will draw refraction diagrams predicting wave crests as they approach different coastlines.
• Waves slow near shallow water, wrapping to the shape of the coastline.

Focus of Wave Energy

• Refraction can focus wave energy into specific spots, creating large waves.
• Underwater ridges cause waves to slow and focus energy over them, leading to bigger waves.

Coastal Changes and Sediment Impact

• Headlands draw wave energy, causing erosion and larger sand grains on beaches.
• Bays with less wave energy accumulate smaller sand grains, creating different beach types.
• Seasonal changes in wave energy can mimic differences similar to winter and summer beaches.

Conclusion

• Understanding wave refraction helps explain coastal wave patterns and their impact on beach formation and surfing conditions.
• For further clarification, students are encouraged to reach out via email.