1.1. On a beach popular with surfers, one is watching a buoy move up and down with the waves, in Figure 1. 

Figure 1

She decides to plot a graph of how the height of the buoy varies with time - this is Figure 2.

Figure 2

Using a stopwatch, she measures the time from the buoy at its highest point to the peak of the 7th and smallest wave.

This takes 24.5 s.

Calculate the frequency of the waves.

Give your answer to 2 significant figures.

   Frequency (2 significant figures) = .................................... Hz

1.2. The surfer knows the distance to the buoy from the shore. 

Describe a method by which the surfer could determine the speed of the waves accurately.

1.3. The surfer determines that the wave speed is a value between 3.5 m/s and 4.5 m/s.

Calculate the possible range of wavelengths of the waves.

Give your answers to 2 significant figures.

 Wavelength is between .................. m and .............................. m

1.4. Suggest why the surfer could only give a range of values for wave speed.