Preparing for Lower Sixth Physics #15: The wave equation

I spotted this interesting wave pattern looking down from Dunnottar Castle. There was a strong wind blowing in waves as shown and yet they bent round the corner behind the rock. This is an example of knife-edge diffraction, rather than diffraction through a narrow gap. Only the latter is on the course. However, once the waves bent round the corner, they got closer together as they went on. This is clear on the photograph. The wind blown waves and the diffracted waves must have the same frequency because they are the same waves - caused by the same thing.

The wave equation states:   wave speed = frequency x wavelength.

So if the frequency remains the same but the wavelength decreases, the speed of the waves must have decreased. They have probably slowed down due to friction on the seaweed.