6.6 Waves

Notes

A wave transfers energy through water; the water itself moves in small circles.

• Parts: crest, trough, wavelength (crest to crest), wave height (trough to crest), period (time between crests).
• Wave speed $\displaystyle v = \frac{\lambda}{T}$ where $\lambda$ is wavelength and $T$ is period. Example: wavelength 60 m, period 10 s gives $6$ m/s.
• Wind speed, duration and fetch (distance over open water) set wave size.
• Waves approaching a beach slow and break when the water is shallow. Waves bend (refract) to hit the shore at an angle, producing longshore drift.
• Tsunamis are long-wavelength waves caused by seafloor earthquakes, landslides or volcanoes, not by wind or tides.