Is sound wave a transverse wave?

[sophiecentaur]

I can't be bothered to read what the AQA says this week (and they will probably say something different next week), but as sophiecentaur said, the bald statement "Sound waves are longitudina" will satisfy the kid with no interest in science who wants to scrape a C grade (and it will also satisfy teachers with the same objectives!) - but if a bright kid actually plucks a guitar string (or even twangs a ruler on a desk) and observes what happens, he or she is likely to get confused![/QUOTE

Where are you getting this information from? In AS specs kids study SHM and waves in strings in considerable detail.They know that both transverse as well as longitudinal vibrations of the string the ruler, or whatever it is sets up longitudinal waves in the surroundings which, depending on the frequency, can be detected as sound. I rarely see anyone get confused by that. Have you actually met any teachers who have the objectives you alluded to?

Well, if he hasn't, i certainly have. Plenty of teachers enter secondary Science education with nothing more than a GCSE Double award C grade in Physics and Chemistry plus, perhaps a degree in Biology. They are delighted at every student who gets C and above and very often, wouldn't spot a potential First Class Hons in Physics because they just don't know enough. It's not their fault; it's the system and they need a job. I never met one of them who actually wanted to be delivering Physics.

At AS, quite recently, kids were hit, first of all, with Fundamental Particles - involving the classification of particles in terms of Quarks. This was before they even knew the definition of Momentum or what an electron Volt was. A shameless bit of 'bums on seats' if ever there was one. Can you justify that?

 

[voko]

"Sound waves are longitudinal" (P1.5.1b AQA physics)

I have no idea what kind of physics this "AQA Physics" is, but it is definitely not the physics that applies to my universe. In my universe, sound propagates in solids just as well as it does in fluids, and propagation in solids involves transverse waves.

The argument "let's not confuse the uneducated inquirer and let's feed him some half-truth and stick with it", even when the inquirer has specifically asked for the other half of the truth, would be received well in the Middle Ages, but now it feels distinctly dated.

 

[dauto]

I think it's well understood by all here that ultrasound is sound and we could go for more detailed definitions such as defining "sounds which are audible to humans" or to bats or to any other animal species. But I don't want to get involved in semantics but want to see OPs question answered at a suitable level.
I'm assuming that the OP is currently at a level which is equivelent to GCSE or perhaps AS or A level (UK qualifications).If so the specifications require that students should understand that....."Sound waves are longitudinal" (P1.5.1b AQA physics)

Can you translate those qualifications into something that makes sense?

 

[jerry0696]

I think it's well understood by all here that ultrasound is sound and we could go for more detailed definitions such as defining "sounds which are audible to humans" or to bats or to any other animal species. But I don't want to get involved in semantics but want to see OPs question answered at a suitable level.
I'm assuming that the OP is currently at a level which is equivelent to GCSE or perhaps AS or A level (UK qualifications).If so the specifications require that students should understand that....."Sound waves are longitudinal" (P1.5.1b AQA physics)

A level
i just want to know the truth not what books want me to know

so is sound wave a transverse wave in solid?

 

[sophiecentaur]

Three modes of transmission are possible in a solid - longitudinal, transverse and surface. It depends upon how you launch the wave as to what you will get. The only thing to remember is that fluids do not support transverse vibrational waves.

 

[voko]

It should also be added that sound propagation in solids is audible directly. There is a mechanism known as "bone conduction", where sound propagates through the scull bones directly into the inner ear. This mechanism is responsible for the surprise when we hear our own voices recorded: they appear higher than we are accustomed to. This is because the bone conducts the lower tones better than air.

Bone conduction most definitely uses both longitudinal and transverse waves.

This mechanism is employed in hearing aids and some special equipment such as underwater communications. It was recently used with Google Glass.

So sound is most definitely not longitudinal waves only, no matter what some dumbed down teaching standards would want us to believe.

 

[dauto]

A level
i just want to know the truth not what books want me to know

so is sound wave a transverse wave in solid?

In a solid you may have both transverse sound waves (called s-waves) and longitudinal sound waves (called p-waves). On a (Newtonian) liquid or gas you only get longitudinal sound waves. Non-Newtonian fluids may behave more like solids at times and might sustain s-waves as well.

 

[jerry0696]

In a solid you may have both transverse sound waves (called s-waves) and longitudinal sound waves (called p-waves). On a (Newtonian) liquid or gas you only get longitudinal sound waves. Non-Newtonian fluids may behave more like solids at times and might sustain s-waves as well.

thank you

 

[Dadface]

Well, if he hasn't, i certainly have. Plenty of teachers enter secondary Science education with nothing more than a GCSE Double award C grade in Physics and Chemistry plus, perhaps a degree in Biology. They are delighted at every student who gets C and above and very often, wouldn't spot a potential First Class Hons in Physics because they just don't know enough. It's not their fault; it's the system and they need a job. I never met one of them who actually wanted to be delivering Physics.

At AS, quite recently, kids were hit, first of all, with Fundamental Particles - involving the classification of particles in terms of Quarks. This was before they even knew the definition of Momentum or what an electron Volt was. A shameless bit of 'bums on seats' if ever there was one. Can you justify that?

Perhaps you have not met many teachers. The ones I have known can spot potential and would certainly not be delighted if a student who they knew to be capable of getting an A star ended up getting a C.
I don't understand the points you made in your second paragraph. All the schools and FE colleges I know require that students have a good pass at GCSE Physics before they are allowed on to an AS course.They would already have a good working knowledge of momentum because they would have studied it at GCSE. Of course a good teacher would do a recap of the subject at an appropriate time during the AS studies. That recap and the introduction of the eV would be covered at appropriate points during the studies.

 

[Dadface]

I have no idea what kind of physics this "AQA Physics" is, but it is definitely not the physics that applies to my universe. In my universe, sound propagates in solids just as well as it does in fluids, and propagation in solids involves transverse waves.

The argument "let's not confuse the uneducated inquirer and let's feed him some half-truth and stick with it", even when the inquirer has specifically asked for the other half of the truth, would be received well in the Middle Ages, but now it feels distinctly dated.

Bearing in mind that one should consider the the present educational level of any enquirer when answering a question it is a universe shared by many educational establishments organisations and books most being very prestigious.A quick search threw up the following, on just the first page
1.Salford Universities learning resource for GCSE describe sound waves as being longitudinal
2.Indiana university refer to it as a pressure wave.
3.Canadas Science and Technology Museum described sound as being a vibration or wave of air molecules
4.The Glen Research Centre of NASA describe sound as being a sensation created in the human brain in response to small pressure fluctuations in the air.

Of course one should try to provide any enquirer with additional information asked for. The fact that there are different modes of vibration in solids has never been disputed here.

 

[Dadface]

Can you translate those qualifications into something that makes sense?

GCSE stands for general certificate of education. Students study different subjects at GCSE and are examined, the finals usually being when they are fifteen or sixteen.
Students who continue their studies usually specialise in a smaller number of subject four being the average. AS stands for advanced supplementary and is a one year course.A stands for advanced level and is an additional year after AS.
Amongst other things most universities require three good passes at A level.

 

[kira506]

but is sound transverse ,longitudinal or both in solid??
everyone is telling me that sound can only be longitudinal (my teachers)

your teachers tell you that because that's what's in your curriculum (same here ) so I suggest that you stick to what your teachers say in exams and scolastic stuff but know and understand the truth

 

[Dadface]

It should also be added that sound propagation in solids is audible directly. There is a mechanism known as "bone conduction", where sound propagates through the scull bones directly into the inner ear. This mechanism is responsible for the surprise when we hear our own voices recorded: they appear higher than we are accustomed to. This is because the bone conducts the lower tones better than air.

Bone conduction most definitely uses both longitudinal and transverse waves.

This mechanism is employed in hearing aids and some special equipment such as underwater communications. It was recently used with Google Glass.

So sound is most definitely not longitudinal waves only, no matter what some dumbed down teaching standards would want us to believe.

It certainly sounds faesible that bone conduction involves different modes of vibration and surely transverse vibrations must be included. Take care though when assuming too much. I'm referring to the work on hearing through bones being carried out by Professor Puria at Stanford University.
The team found that the application of inertial bone stimulation only resulted in hearing loss but when bone compression was included hearing jumped up. I think this is work in progress.

And why so scathing about work being dumbed down as you describe it? Simplifying to a relevant level is one of the ways education can be delivered effectively. As for this discussion I think that the syllabi cover sound studies at a proper and useful level. Students should be informed when things are simplified so they have the opportunity of looking at stuff in greater depth.

 

[Dadface]

your teachers tell you that because that's what's in your curriculum (same here ) so I suggest that you stick to what your teachers say in exams and scolastic stuff but know and understand the truth

Good advice.

 

[sophiecentaur]

Good advice.

Pragmatic I agree but what do you say to the student who is offended that he was told the 'wrong' stuff, earlier on? They learn to be suspicious of everything they are ever told. Can't be a good thing for their confidence.
Just a bit of thought in how you tell them things can prevent that sort of thing happening. There are plenty of suitable ways of describing the propagation of sound which do not lead to the OP's problem. Unfortunately, specifications do not seem to include such subtleties. Doesn't the evidence of low UK performance in international league tables support my concern?

btw, unless things have changed greatly in the last year or two, it is quite possible for kids to find themselves on an AS Physics course with no more than a reasonable pass in GCSE Double Award. So they may never (and I mean never) have been taught by a Physicist before their AS course. Momentum is just one of the things that the Double Award leaves out. I know there are many 'good' schools where such problems don't arise but taking the three Sciences separately usually seems to require extra curricular time and more work for the Science staff.

 

[voko]

And why so scathing about work being dumbed down as you describe it? Simplifying to a relevant level is one of the ways education can be delivered effectively. As for this discussion I think that the syllabi cover sound studies at a proper and useful level. Students should be informed when things are simplified so they have the opportunity of looking at stuff in greater depth.

This is not just simplifying, this is over-simplifying to the level when it is just wrong. "Audible by humans" is wrong. "Longitudinal only" is wrong. This is not a simplification, this is misinformation.

 

[Dadface]

Pragmatic I agree but what do you say to the student who is offended that he was told the 'wrong' stuff, earlier on? They learn to be suspicious of everything they are ever told. Can't be a good thing for their confidence.
Just a bit of thought in how you tell them things can prevent that sort of thing happening. There are plenty of suitable ways of describing the propagation of sound which do not lead to the OP's problem. Unfortunately, specifications do not seem to include such subtleties. Doesn't the evidence of low UK performance in international league tables support my concern?

btw, unless things have changed greatly in the last year or two, it is quite possible for kids to find themselves on an AS Physics course with no more than a reasonable pass in GCSE Double Award. So they may never (and I mean never) have been taught by a Physicist before their AS course. Momentum is just one of the things that the Double Award leaves out. I know there are many 'good' schools where such problems don't arise but taking the three Sciences separately usually seems to require extra curricular time and more work for the Science staff.

I think the main problem, as you pointed out earlier is the shortage of well qualified staff, including those with enough experience to guide new colleagues.

 

[Dadface]

This is not just simplifying, this is over-simplifying to the level when it is just wrong. "Audible by humans" is wrong. "Longitudinal only" is wrong. This is not a simplification, this is misinformation.

I have a suggestion. Look at the syllabi of different exam boards and other relevant organisations and suggest to them that they tweak their specs. For example part of an AQA spec states:

...sound waves are longitudinal...

This could be added to slightly, for example:

...sound waves are longitudinal but candidates should also be aware that in solids sound waves can be transverse as well as longitudinal...(I'm sure the wording can be improved)

If you give it a go please let us know how you get on.

 

[sophiecentaur]

I think the main problem, as you pointed out earlier is the shortage of well qualified staff, including those with enough experience to guide new colleagues.

There is an excuse, of sorts, for the lack of qualified staff but there is no excuse for poor specifications and for education policies that build in unnecessary problems.
If the UK want good teachers then they just need to pay enough to make the profession attractive to enough bright people and for the Great British Public to realize that Education is something to aspire to. The recent surge in better quality graduates, due to the lack of other jobs, may produce an improvement in the medium term but, once the better jobs become available elsewhere, we will be back to an intake of teachers for whom the profession has been largely a second choice.
The present government doesn't seem to know what it means when it talks about 'qualified' or 'unqualified' teachers, for a start. We don't need any David Starkeys in charge of classes in our schools. (ref. that disastrous TV prog).