As ocean waves approach shore, their velocity decreases. How does a decrease in velocity affect the frequency and wavelength of the waves entering the shallow water? A. frequency increases and wavelength decreases B. frequency decreases and wavelength increases C. frequency stays the same and wavelength increases D. frequency stays the same and wavelength decreases
The Correct Answer and Explanation is:
Correct Answer: D. Frequency stays the same and wavelength decreases
Explanation:
As ocean waves move from deep water into shallow water, they experience a change in speed due to the interaction between the wave and the ocean floor. Specifically, the wave velocity decreases in shallow water. To understand how this affects frequency and wavelength, we must consider the relationship between these wave properties.
The basic wave equation is: v=f×λv = f \times \lambdav=f×λ
Where:
- vvv is the wave velocity (speed),
- fff is the frequency,
- λ\lambdaλ is the wavelength.
This equation shows that wave speed is equal to the product of frequency and wavelength. In most natural systems like ocean waves, the frequency is determined by the original source of the wave, such as wind over deep water, and it does not change as the wave enters shallower areas. This is because the wave continues to oscillate at the same rate per second, regardless of water depth.
However, as the wave moves into shallow water and its speed decreases, and the frequency remains the same, the wavelength must decrease to keep the relationship consistent. That means the distance between successive wave crests becomes shorter.
This is why, near the shore, waves are more tightly packed and appear closer together. Their wavelength shortens, but their frequency remains constant.
This behavior also explains why waves become steeper and may eventually break near the shore — as the wavelength shortens and energy is compressed into a smaller space, the wave height increases and instability forms.
Thus, when ocean waves slow down in shallow water:
- The frequency stays the same,
- The wavelength decreases.
So, the correct answer is D.
