Re: Episode from the history of physics.

On Apr 7, 1:38 pm, v...@xxxxxxxxxxxx wrote:
On Apr 7, 1:57 pm, "PD" <TheDraperFam...@xxxxxxxxx> wrote:

On Apr 7, 12:24 pm, v...@xxxxxxxxxxxx wrote:

<snip>

It is common knowledge that the media in which a wave is produced or
is present is the cause of wave characteristics such as interference
and diffraction.

I notice that you refer to a high school physics site for what you
consider to be "common knowledge". What you consider to be "common
knowledge" is in fact "common error".

Are you saying that high school physics books are wrong?

First of all, this is a high school physics *site*, not a high school
physics book. There is substantially more editorial care with a
physics book than with a physics site.

Secondly, the site *specifically* restricts the discussion to the
topic of sound, not waves in general. It also says that, *in the case
of sound*, interference is a phenomenon that is observed to happen
*when* two waves happen to meet in the same medium. Since *sound*
waves always occur in a medium, then a medium will be present when two
sound waves meet. This does NOT mean that you should interpret this to
mean that interference occurs in any way *because of* the medium, NOR
does it mean that you should conclude that mention of a medium will
always be made in waves of any description. There is *nothing* said,
even in those poorly edited physics pages (you get what you pay for),
that says that interference does not occur without a medium present;
in fact, it doesn't deal with non-sound situations at all.

Can you show
me a more dependable source that says that interference and
diffraction involving sound waves is not caused by the medium through
which they are traveling.

Yes, certainly. Would you like a reading reference? The Berkeley
series of introductory physics books has a lovely volume about Waves
(McGraw-Hill College, ISBN 0070048606) that gives a *much* more
dependable presentation of what causes interference than the pages you
referenced. Though, apparently you have difficulty reading things that
aren't there in the web pages, so I'm not sure how you'll fare with
the book.

We are not talking about light waves,
gravitional waves, quantum mechanical waves or other waves that you
seem to be convinced don't require a medium. You have already
stipulated that sound waves require a medium. Now I'm trying to see
why in the world you don't think that the medium causes basic wave
characteristics.

Because those wave characteristics are derived from the wave equation,
which operates just as well in cases where a medium is present as when
a medium is not present.

Look, if you started to tell me that laying eggs is what defines birds
and that birds are birds because they lay eggs, I would point to a
turtle. If you then asked me if I denied that chickens lay eggs or
that chickens are birds, I would say of course not. But that doesn't
mean that laying eggs defines an animal to be a bird, and it doesn't
mean that a turtle is a bird. Just because sound, which exhibits
interference, involves a medium, does NOT mean that things that
exhibit interference have that interference caused by a medium.

You admit that the medium must be present for there
to be a wave,

Only for *some* waves.

but you refuse to admit that it also causes the wave's
characteristics.

Right. It's the physical laws that cause the waves. The fact that for
sound waves, the physical laws involve a medium, is purely specific to
that case and does not mean the medium causes the wave
characteristics. Exactly.

PD

Unbelievable.

Vern


.

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