When water waves travel from a deep region

[Hyperreality]

When water waves travel from a deep region to a shallower region, its wavelength decreases, explain fully why this happens.

This problem has appeared in my recent examination and I'm not sure if the examiner will accept my explanation:

In the shallow region, there is more "ground", so when waves enter from a deep region to the shallow region, it "hits the extra ground", and therefore its speed decreases. Since the frequency of the wave stays constant, its wavelength is decreased.

I know the first part of my explanation is probably not the examiners are looking for, the explanation they are likely to accept is:

The shallow region are higher than the deep region, so when the waves enter the shallow region, it loses kinetic energy in terms to gain potential energy.

The marking schedule for this question is likely to ranges from Not Achieve, Achieve, Merit to Excellence (this is New Zealand's new education system). What kind of grades would I be likely to get?

 

[HallsofIvy]

"The shallow region are higher than the deep region"

This doesn't really make sense to me. I assume you MEANT the bottom is higher. The water itself if NOT going up (sea level is sea level!) so it is not gaining potential energy.

Honestly, you first answer seemed better to me. You might phrase it more precisely: the waves are losing energy (and so speed) because the water is "rubbing" against the bottom more and losing energy to friction.

 

[M98Ranger]

It is difficult to accurately predict the grade you may receive for this response, as it ultimately depends on the specific criteria and expectations set by the examiner. However, it is important to note that the first part of your explanation, while not entirely incorrect, may not fully address the concept of wavelength decreasing in a shallow region. The second part of your explanation is more accurate, as it highlights the role of potential energy in the decrease of wavelength.

Based on the given marking schedule, if your response effectively explains the concept of wavelength decreasing in a shallow region and accurately describes the role of potential energy, you may receive a Merit or Excellence grade. However, if your explanation is not as thorough or accurate, you may receive an Achieve grade. It is important to provide clear and concise explanations for scientific concepts in order to receive a higher grade.