# Refraction of light -- What is the best description for 10th grade physics students?

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Is the eigenfrequency just another term for the natural/resonant frequencies of some system, or is it different?
Yes, it's the resonant frequencies of the system.

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Is Huygens Principle rubbish?
Has anyone suggested that it is? I can't see that the teacher was presenting any form of Huygens. There are a number of analogies to show how a wave front can change direction but they do not involve a 'reason' for change of wave speed - and neither does Huygens. In fact there are many theories from the past which are described, these days, in terms of what has been found out subsequently.

Homework Helper
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The term "rubbish" was applied to the wheel and axle explanation of the result of Huygens on the wave front. The speed change was a given at that point. It seemed to me a clever explanation but apparently was not admired by @Dr_Nate; I was questioninq both his analysis and his use of the word.

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For the wave equation in 3 (spatial) dimensions the Huygens principle is correct. It's known as the regarded Green's function.

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For the wave equation in 3 (spatial) dimensions the Huygens principle is trtcorrect. It's known as the regarded Green's function.
I have to ask you at what age were you introduced to Green’s function and the maths of a wave function. How you would have dealt with it in tenth grade.
it’s a real potential failing of PF that contributions to virtually any thread are subjected to intellectual inflation and the ball is so often stolen from the OP.
How to present hard concepts at all levels is a very valid talking point. Perhaps the levels of posts should be policed stronger and the meaning of “off topic” could be re-examined.