Figure 16.38

[ericmazur]

"A standing wave is a stationary harmonic wave with an aptitude that varies like a sine." muddles the concept of "amplitude" Better "A standing wave is a stationary sinusoidal wave."

Sears for amplitude and make sure that this problem doesn't crop up elsewhere

[JohnDenker]

We agree that it's not good to abuse the word "amplitude".

Meanwhile, there are at least two additional, independent problems here:

A standing wave doesn't need to look like a sine wave. Counterexamples include:

• Standing wave on a chain with non-uniform tension (due to its own weight).
• Standing wave in a conical bore e.g. oboe or saxophone, among many others.
• et cetera.

I know this is a chapter on waves in 1D, but the term standing wave should be defined in a way that works in any dimension, from one on up. So additional examples include:

• Standing waves on the surface of a circular swimming pool.
• Standing waves on the head of a round drum.
• Acoustical or electromagnetic standing waves in a non-rectangular cavity.
• Stationary atomic orbitals such as 2s or 3px.
• et cetera

Also a standing wave doesn't need to be harmonic.

• A chain under its own weight is markedly anharmonic at easily-achievable amplitudes.
• The strings of many musical instruments are perceptibly anharmonic at easily-achievable amplitudes.
• Et cetera.

The term "standing wave" is (for once!) not an idiomatic expression. That is, you can figure out the meaning just by looking at the words. It is any wave that isn't a running wave.

Perhaps most importantly of all, it is not good practice to define "standing" in terms of "stationary". It would make just a much sense (i.e. no sense at all) to define "stationary" in terms of "standing".

• It is bad practice pedagogically to define words in terms of words, because it incites rote memorization. It is much better to focus on ideas, not mere words.
• It is bad practice operationally, insofar as it can lead to circular definitions or dangling definitions.

In this case term "stationary" has not been defined in the book AFAICT. It is not mentioned in the index. It is a highly technical term, and students were not born knowing what it means.

Possibly constructive suggestion:

My best effort at defining "standing wave" is at: https://www.av8n.com/physics/wave-intro.htm#sec-standing-wave