Chapter 30, Problem 18RQ

To determine

The reason behind the fact that the waves become taller as they enter shallow water.

Answer to Problem 18RQ

The reason behind the fact that the waves become taller as they enter shallow water is the change in shape of the wave from orbital to elliptical.

Explanation of Solution

When wave moves from deep water to shallow water, they change form. In deep water, the wave motion is orbital. In shallow water the orbital motion becomes elliptical. This is because of the contact of the wave with the bottom surface.

This change from orbital to elliptical shape decreases the wave speed. As incoming waves continues to advance, the distance between the waves decreases, causing wave height to increase. That is waves become taller. When waves reach a critical height, they break and crash into the surf zone.

Conclusion:

Therefore, the reason behind the fact that the waves become taller as they enter shallow water is the change in shape of the wave from orbital to elliptical