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Hi all-
I totally do not understand these remarks. The "ray" picture
arises from an approximate solution to the wave equation, increasingly
good as the frequency increases.
When we talk about the suns rays we are falling back upon the
existence of such solutions. They are practically useful. Acousticians
use ray tracing to "calculate" acoustical paths. Lens designers can use
ray tracing for lens design. And so forth.
This is much more than mere pedagogy.

On Wed, 31 Jan 2001, Jim Green wrote:


You could just say that in physics it is sometimes helpful to use
an artificial language because it sometimes paints a clearer picture --
incorrect but clearer and easier to understand -- as long as we keep in
mind that the language is really incorrect.

eg we talk about the Sun's rays as if there were pencil lines streaming
from the Sun -- there are no such things but this may present a helpful picture

When we talk about Gauss' Law it is certainly helpful to picture lines, but
such lines really do not exist. Just saying this makes the explanation
palatable to your HS students while not teaching falsehoods to them.

When we discuss lenses, it is sometimes helpful to picture rays --
sometimes helpful to consider ocean waves -- or even a marching band -- to
explain what we see.

When we talk about diffraction it is helpful to talk about sinusoidal waves.

The truth is that no one has the foggiest idea of what light is -- we talk
about photons when that idea is helpful and waves when that idea is helpful
to solve problems. But light is neither corpuscular or a wave -- although
it acts like one or the other at times.

While [Jane] Austen's majestic use of language is surely diminished in its
translation to English, it is hoped that the following translation conveys
at least a sense of her exquisite command of her native tongue.
Greg Nagan from "Sense and Sensibility" in
<The 5-MINUTE ILIAD and Other Classics>