Phase vs Frequency

[Mark R]

A journal recently sent me a scientific paper for comments.

I've been struggling with it for several days, and I've just worked out why.

The word "phase" must be one the writer's favorite words, given how much he/she uses it. The trouble is that what they actually mean is "frequency".

It's all now clear, and I've got at least 1 constructive comment to make 🙂

 

[PsiStar]

Are you referring to something like phase modulation versus frequency modulation.

Or ... why did you start a thread?

 

[SagaLore]

What's the article about?

 

[TuxDave]

Give us an example...

 

[Joseph F]

Give us an example...

This.

 

[Mark R]

Give us an example...

The bottom of the figure shows the values for water and NAA peak
phases generated by the post-processing software.

The figure axis is even labelled "frequency".

 

[PottedMeat]

The bottom of the figure shows the values for water and NAA peak
phases generated by the post-processing software.

The figure axis is even labelled "frequency".

maybe they accidentally replaced all the frequencies with 'phase'?


...or they don't know what they're talking about

 

[Howard]

That's crazy. Call into question their academic credentials, with vigor and spite.

 

[Gibson486]

well, if the phase changed periodically....

 

[Jeff7]

Future Star Trek writer?

 

[PsiStar]

unclear still it is

Is phase a form of some substance or state that occurs relative to a frequency of a something 😕

 

[Dirigible]

That's crazy. Call into question their academic credentials, with vigor and spite.

Oooo! I want to do everything with vigor and spite from now on!!

 

[Gintaras]

Don't pee on phase

 

[Paperdoc]

The bottom of the figure shows the values for water and NAA peak
phases generated by the post-processing software.

The figure axis is even labelled "frequency".

As a physical chemist, what I think is being said is this. The mixed liquid system has been allowed to separate into two different immiscible (that is, they don't mix) layers properly called "phases" in that field. One is mainly water, and the other contains something called "NAA". That's obviously an acronym for a material under study, and I assume its full identity is disclosed elsewhere in the paper. The caption, I suspect, is for a spectrum showing intensity of a spectral absorption peak on the vertical axis, and frequency of the light / radiation along the horizontal axis. I would expect the purpose of the graph is to show that the "NAA phase" contains certain absorption peaks absent in the pure water phase; hence, those peaks are characteristics of the spectrum of NAA. I expect the interpretation of those peaks then leads to some discussion of the composition or properties of this NAA.

In most fields of Chemistry and physics we use the word "phase" to label the possible physical states of matter: gas phase, liquid phase, and solid phase. Derived and extending from that, it is normal in Chemistry to use the word "phase" to label different layers as they separate. It is applied to solid versus liquid, oil versus water, etc. I suspect that is the context in which the paper you've been reading uses the term.

 

[dave_the_nerd]

Are they a native english speaker? They might have just learned that word wrong.

 

[Farmer]

At least in physics, often times "phase" refers to the argument of a complex exponential, or the complex exponential itself

.

For instance, if I had

,

I could say something like "\psi_2 differs from \psi_1 only by a phase," or something along those lines. Many times in physical applications, that phi term is actually equal to either a position frequency times a position or a time frequency times a time, for instance

,

or

,

for instance in a plane wave

.

That is the extent of my understanding as to what he means by these two terms. I also study condensed matter systems, but mostly vibrational properties, where plane waves are fairly fundamental. Paperdoc may be more spot on, but that would be revealed if we knew more context, like the topic of the paper or what journal it is meant for.

 

[PhlashFoto]

Maybe it's just a phase the writer(s) are going through....

 

[Mark R]

As a physical chemist, what I think is being said is this. The mixed liquid system has been allowed to separate into two different immiscible (that is, they don't mix) layers properly called "phases" in that field. One is mainly water, and the other contains something called "NAA".

You're the closest.

This was a paper about NMR spectroscopy. The paper was about environmental effects on the resonance peaks of water and NAA.

They were exploring the changes of resonant frequency of both the water and NAA spins. They described the changes in frequency as "phase shifts".

At first I wondered whether they were using some clever method of estimating the frequency shift by actually measuring phase shift (which can be done with appropriate data acquisition tools and software), avoiding the need for a full Fourier transform type acquisition. But there was nothing about that in the methods, or anywhere else in the paper.

Then I realised....