How does a light wave change when travelling from water to air?

[misterc]

I'm a high school physics teacher and this was a question posed to my Honors Physics class.

[Simplified]
A light wave travels from water to air. Which of the following variables does NOT change between the mediums?"
A. speed
B. wavelength
C. amplitude
D. frequency

I intended the answer to be frequency. But, upon further analysis, I couldn't give a good answer as to whether the amplitude changes or not. I was thinking in terms of classical waves (e.g. strings, sound, water). But, I specifically used a light wave. In perusing PF, I saw a previous thread discussing whether light as a photon has an amplitude. I'll admit the discussion got really deep, but the conclusion seemed to be that amplitude doesn't quite apply to a single photon, and for a light "wave", intensity would be a better descriptor. However, I did say amplitude.

The students know about energy/intensity vs. amplitude, but not really about light being wave and particle. They may be familiar with the concept though. My question is whether option C was ambiguous enough to warrant accepting it as an answer.

 

[jerromyjon]

Wavelength and frequency are linearly related. Amplitude only depends on interference in photons, as far as I understand it.

 

[axmls]

See this question: http://physics.stackexchange.com/qu...gth-change-as-light-enters-a-different-medium

There's no need to invoke photons.

 

[Dale]

To my knowledge, C would not be a correct answer. The amplitude does change.

 

[blue_leaf77]

The amplitude should change as a consequence of EM boundary conditions.