Final answer:
A collapsing breaker occurs when waves break right at the shoreline due to shoaling. In a harbor with a 50.0 m-wide opening, wave diffraction will determine the protected angles against wave action for boats.
Step-by-step explanation:
The type of breaker that forms when the wave build-up and breaks right at the shoreline is known as a collapsing breaker. As waves reach shore, the water depth decreases, leading to a compression of wave energy due to shoaling, resulting in higher and steeper waves.
Regarding the protection against wave action inside a harbor with an opening of 50.0 m and ocean waves of 20.0 m wavelength approaching straight on, the phenomenon of wave diffraction must be considered to determine the angles at which boats are most protected. Diffraction will cause waves to bend and spread out as they pass through the opening, potentially impacting areas within the harbor that are not directly aligned with the incoming waves.
Using principles of wave diffraction and interference, it can be calculated at which angles relative to the incident wave direction boats will find a safe haven from wave action. As this is a physics-based wave mechanics problem, an exact calculation would require application of diffraction formulas and knowledge of additional variables such as the harbor's shape and the specific wave conditions.