Given,
The distance between the two docks, d=40.0 m
The wavelength is described as the distance between the two adjacent crests.
Here λ is the wavelength.
From the figure, there are 4 wavelengths between the docks.
Thus the wavelength of the wave is given by,
![\lambda=(d)/(4)](https://img.qammunity.org/2023/formulas/physics/college/75ppwhgbsby9s8w6cvqses3ir9w5i70u0t.png)
On substituting the known values,
![\begin{gathered} \lambda=(40)/(4) \\ =10\text{ m} \end{gathered}](https://img.qammunity.org/2023/formulas/physics/college/kmebqh2btdvxpuggg7cbodbhjpkg9sm2sj.png)
Thus the wavelength is 10 m