Do light and sound waves roll up and break like ocean waves?

[Dilema]

When sea waves approach the shore they roll up and break due to different velocities of water layers formed due to the gradual change in water depth. The highest wave peaks move faster than all other layers and thus falls down. All other layers fall the same way but in a delay. this ends up with wave rolling up when approaching the shore.

Does light and sound wave have a similar phenomenon? and then how it looks like or how it sounds?

 

[cosmic onion]

Hi there. This is my first attempt at a reply. I hope others can correct me if I am wrong. As sounds waves are compressions and rarefactions (compressions and streaching) in air. Wouldn'the the collapse you talk about occur when we hear a sonic boom of an aircraft breaking the sound barrier ?. As for light this would be a different case as its speed is a fundamental constant of nature (no eather to support a collapse).

 

[tech99]

When sea waves approach the shore they roll up and break due to different velocities of water layers formed due to the gradual change in water depth. The highest wave peaks move faster than all other layers and thus falls down. All other layers fall the same way but in a delay. this ends up with wave rolling up when approaching the shore.

Does light and sound wave have a similar phenomenon? and then how it looks like or how it sounds?

I sometimes think that the breaking wave is a conversion from a transverse wave, going up and down, into a longitudinal wave, going forward and back.
Such transitions occur with EM waves with a receiving antenna wire, where an incoming transverse EM wave is partly converted to a longitudinal wave on the wire. In sound, a transverse wave on a string is converted to a longitudinal wave in the air.
There are a number of situations with EM waves, light etc, where the medium no longer supports a transverse wave, and we get an evanescent wave, so called. This includes when the wave enters a metal pipe that is "too small" and at a surface where there is total internal reflection.

 

[I like Serena]

When sea waves approach the shore they roll up and break due to different velocities of water layers formed due to the gradual change in water depth. The highest wave peaks move faster than all other layers and thus falls down. All other layers fall the same way but in a delay. this ends up with wave rolling up when approaching the shore.

Does light and sound wave have a similar phenomenon? and then how it looks like or how it sounds?

With light we have for instance Cherenkov radiation, which happens when particles enter a medium where their speed exceeds the speed of light in that medium.
(Contrary to popular belief, the speed of light is not an absolute limit - it's the theoretical speed of light in vacuum that is.)
Although, to be fair, that's not about actual light going through mediums with decreasing light speeds, but about particles with speeds approaching the speed of light.

 

[jerromyjon]

When sea waves approach the shore they roll up and break due to different velocities of water layers formed due to the gradual change in water depth.

Something to think about is the fact that water is not very compressible so that is why it rolls up and crashes when it reaches a shoreline, sound waves are different in the fact that they do compress and stretch the matter they travel through...

 

[Clausen]

When sea waves approach the shore they roll up and break due to different velocities of water layers formed due to the gradual change in water depth. The highest wave peaks move faster than all other layers and thus falls down. All other layers fall the same way but in a delay. this ends up with wave rolling up when approaching the shore.

Does light and sound wave have a similar phenomenon? and then how it looks like or how it sounds?

This is how it looks with light:

The "photonic Mach boom" is produced when a light wave passes through two different media, where one has a slower velocity of propagation than the other.

 

[cosmic onion]

Fantastic, so you do get a light boom.

 

[sophiecentaur]

Something to think about is the fact that water is not very compressible so that is why it rolls up and crashes when it reaches a shoreline, sound waves are different in the fact that they do compress and stretch the matter they travel through...

Ocean Waves are different from sound and EM waves - or even waves on strings. They are Surface Waves, which involve transverse AND longitudinal displacement (particles follow an elliptical curve as the wave passes*) and you can get 'overtaking' of the water at the peaks when it falls forward, in front of the lower parts of the wave. This overtaking of the medium can't happen with transverse or longitudinal waves so there is a fundamental difference. In the case of a shock wave, the particles of the medium are pushed forward at a speed greater than the natural wave speed.
* I remember scuba diving over a bed of very long kelp, under some significant swell. There was a finger of rock sticking up above the kelp and I could see the top (from my reference frame) performing a massive vertical circle in front of me. Bizarre. The illusion was magnified by the fact that the kelp was moving with me all the time -just the rock was bolted to the sea bed. It was all very peaceful with no fuss - till I was getting back into the dive boat.

 

[Dilema]

Dear all replayers
1. The different wave velocities in a medium are not sufficient to have wave roll up. You need a force field (like gravitation) to have an equivalent to a water layer falling due to gravity.
2. Remeber the water bath with slits that showing the diffraction and interference the geometrical considerations in bought light and water waves going through slits are the same. This is one of the equivalents that makes us think the light has wave aspect.

 

[CWatters]

1. The different wave velocities in a medium are not sufficient to have wave roll up. You need a force field (like gravitation) to have an equivalent to a water layer falling due to gravity.

So could it happen near a black hole?

 

[tech99]

Dear all replayers
1. The different wave velocities in a medium are not sufficient to have wave roll up. You need a force field (like gravitation) to have an equivalent to a water layer falling due to gravity.
2. Remeber the water bath with slits that showing the diffraction and interference the geometrical considerations in bought light and water waves going through slits are the same. This is one of the equivalents that makes us think the light has wave aspect.

(1) So far as I know we do not have any wave breaking action with EM waves if we use a magnet or a fixed electric field. (I realize we can have polarization effects if the medium is a dielectric). However, I think that the action of receiving and transmitting antennas are equivalent to wave breaking.

 

[sophiecentaur]

1. The different wave velocities in a medium are not sufficient to have wave roll up.

Isn't it more basic than that? To get a breaking phenomenon, you need parts of the medium to overtake other parts. How is that going to happen within the bulk of any medium unless there is a path 'round the outside" (over the top, actually)? It would have to involve Turbulence which is hard to envisage along a uniform wave front. Turbulence happens with supersonic aircraft but I can't see that is the same as a water wave breaking.

 

[Steelwolf]

As I see it, the waves breaking on a beach happens as the base of the wave meets resistance in the form of the sloping seabottom and beach and the top of the wave, still carrying it's same forward momentum is going to go faster than the base of the wave, thus the (as we see it) curl and break of the wave, most of this energy is changed into Sound, both in air and through the ground. Both are physical waves.

The same basic mechanism is happening with both sonic booms and Cherenkov radiation, where the wave that is produced is moving faster than the media it is in can accept thus the crash and boom of the supersonics as the object creating the wave is moving faster than the air can carry that wave and so it is changed radically in volume as the speed energy is dissipated/transformed into something that the air mass can carry, thus no energy loss. Fast becomes Loud.

The same happens with the blue glow of Cherenkov radiation where light ( akin to high energy gamma rays) or particles (akin to cosmic rays but from radioactive sources) are trying to go through a medium with more energy and speed than is allowable and the energy from the slowdown because of this resistance is transformed into a different range of light which we see as a blue glow.

Admittedly, they are all in different regimes, but the basic cause is the same and that is the energy the initial wave carries being more than the wave-form can carry in that medium and that extra energy is transformed into a different but similar form of energy which the media Can support.

 

[sophiecentaur]

The same basic mechanism is happening with both sonic booms and Cherenkov radiation

I can't see how there is any re-ordering of the medium when there is no 'extra dimension' for the material to move through (i.e. the air above the water surface. After a water wave has passed, the water at the surface has actually changed places with water in front and behind. In an ordinary sound wave, the medium returns to the same distribution as it was before the wave went through.
To my mind this is highly significant and it is a different mechanism for resolving the problem of different wave speeds from an ordinary longitudinal wave.

 

[Dilema]

"So could it happen near a black hole?"
I have no idea.
I think in most cases scientists observed a phenomenon and then did the analogy. I do not recall any case of a searching phenomenon to meet analog.
In analogy to mathematics. It is much easier to obtain a derivative than to integrate. The analog is a "derivation" of a phenomenon

 

[snorkack]

For sound, it is shockwaves.

The basis of the phenomenon is that wave velocity depends on the amplitude/phase, such that for sufficiently strong waves the wave crests move faster and overtake the bottoms.

Note that the non-sinusoidal, broken waves can be approached by Fourier transform as combinations of waves with higher harmonics, so frequency is multipled.

Are there any conditions where light gets broken - as in, the waveform is changed by the crests overtaking other phases of the wave? Strong light does feature generation of light harmonics, but does light form shockwaves then?

 

[sophiecentaur]

Note that the non-sinusoidal, broken waves can be approached by Fourier transform as combinations of waves with higher harmonics, so frequency is multipled.

Fourier analysis only applies to single valued functions. After the sea wave has 'broken', there is water 'hanging' over the trough and that corresponds to four[Edit: sorry, Three!] values of displacement at that position. The analogy doesn't apply to any other form of simple wave.
PS Has no one else ever seen a breaking wave and observed that the peak moves out over the trough? No surfers?

 

[ISamson]

When sea waves approach the shore they roll up and break due to different velocities of water layers formed due to the gradual change in water depth. The highest wave peaks move faster than all other layers and thus falls down. All other layers fall the same way but in a delay. this ends up with wave rolling up when approaching the shore.

Does light and sound wave have a similar phenomenon? and then how it looks like or how it sounds?

In my opinion we have to decide whether we have to look at sound and light as particles or waves. I believe this will simplify the question a lot.

 

[jerromyjon]

In my opinion we have to decide whether we have to look at sound and light as particles or waves. I believe this will simplify the question a lot.

From past experience in this forum, the particle/wave aspect only complicates matters and causes confusion!
Sound waves consist of waves in matter they propagate through, having no "substance" of their own to call a "particle".
Electromagnetic waves don't have particle behavior until they interact with matter, and they always travel at the same velocity in any given media so the only thing that could possibly "roll up and break" might be the phase velocity, which can exceed the speed of light but I don't know what visual effects that might incur.

 

[sophiecentaur]

Sound waves consist of waves in matter they propagate through, having no "substance" of their own to call a "particle".

Sound propagation through a solid can be analysed very successfully in terms of Phonons. (link) It's strange that no one 'wants' phonons to the real; they accept that they are only a convenient model and happily get on with "Sound Waves". Photons should have a similar status because they are only one convenient model of EM propagation and interaction.

 

[tech99]

For sound, it is shockwaves.

The basis of the phenomenon is that wave velocity depends on the amplitude/phase, such that for sufficiently strong waves the wave crests move faster and overtake the bottoms.

Note that the non-sinusoidal, broken waves can be approached by Fourier transform as combinations of waves with higher harmonics, so frequency is multipled.

Are there any conditions where light gets broken - as in, the waveform is changed by the crests overtaking other phases of the wave? Strong light does feature generation of light harmonics, but does light form shockwaves then?

If I insert a diode in series with the centre conductor of a coaxial transmission line, I can obtain longitudinal pulses of current rather like a breaking wave, with an average forward motion. But this problem is not simple!

 

[snorkack]

As water waves break, the water level ceases to have a single value.

In a sound wave, is it possible for temperature and pressure to cease having a single value, as the changes of temperature become too fast for equipartition of energy between various degrees of freedom?

 

[sophiecentaur]

As water waves break, the water level ceases to have a single value.

In a sound wave, is it possible for temperature and pressure to cease having a single value, as the changes of temperature become too fast for equipartition of energy between various degrees of freedom?

For a wave to 'break', I think you need it to be tethered in some way, which is how a water wave can have three or more displacement values at some value along the x axis. I say that you cannot have breaking on a free wave. You need a combination of longitudinal and transverse components for your wave to break and for the share of those components to be dependent on the wave amplitude. They are equal for low amplitude waves in deep water but the peakiness increases with amplitude. I don't think there is an equivalent that's not a surface wave. You definitely need some non linearity involved .

If I insert a diode in series with the centre conductor of a coaxial transmission line

I see how you are thinking here but would the diodes introduce a time difference? Is it really the equivalent to having transverse and longitudinal components? Any traveling EM wave is essentially transverse, isn't it? But I guess the effect would only need to occur for a short distance in which the wave energy would be dissipated (as on the beach).

Solids can transmit transverse and longitudinal waves but not gases or liquids. If the modulus of the solid were not isotropic such that the two (long and trans) wave speeds were the same for low amplitudes but non linear so that transverse modulus were higher for large displacements, high amplitude transverse waves could overtake longitudinal waves.
My brain has started to hurt here but why not have a discrete component version of this with a three dimensional lattice of springs (non linear, of course) which would be much more feasible to implement. The sound would, unusually, have to be polarised in the transverse mode. Another thought - how would you measure / display this effect?

 

[nikkkom]

When sea waves approach the shore they roll up and break due to different velocities of water layers formed due to the gradual change in water depth. The highest wave peaks move faster than all other layers and thus falls down. All other layers fall the same way but in a delay. this ends up with wave rolling up when approaching the shore.

Does light and sound wave have a similar phenomenon? and then how it looks like or how it sounds?

This definitely happens for sound.
As sound propagates through air, a small fraction of its energy dissipates - it heats air. Speed of sound in hotter air is greater. Thus, subsequent sound waves propagate faster than the first.

For weak sounds, this effect is negligible. For very loud sounds, the effect is strong enough that after some distance from source the second wave crest runs into the first and combines with it. Such "sound" is called a shock wave. Observationally, shock waves differ from sound waves by having supersonic velocity (relative to unshocked air in front of them), and their velocity increases as they become stronger. (Additional effects come into play when shock is strong enough to heat air to temperatures where it glows).

 

[olivermsun]

To add to what nikkkom says above, anytime you have a wave where the velocity of the particles/material within the waves becomes noticeable with respect to the phase velocity of the waves, then "interesting" things start happening, and you can no longer ignore breaking/dissipation/damping etc. in modeling the wave. Acoustic shocks are an example of how the physical system "avoids" multi-valued variables where they would be aphysical.

 

[jerromyjon]

Additional effects come into play when shock is strong enough to heat air to temperatures where it glows

I pondered the movement of the air relative to sound briefly, but didn't want to say it first. Now you have me pondering how the new rail guns that stream a wave of plasma behind the projectiles sounds...

 

[sophiecentaur]

A shock wave is a localized thing that can only happen near the source. From a spherical source I cannot see how there is a true breaking effect for reasons of symmetry. The turbulence around a wing gives regions with different forward velocities, very like breaking. But that is at the beginning of the life of the wave, not like a sea wave breaking at the end of its life.
I think that some contributors here are confusing wave speed with speed of the medium.

 

[nikkkom]

A shock wave is a localized thing that can only happen near the source.

Google NWFAQ. A very good read on shocks.

 

[tech99]

I thought originally that the breaking action resulted in mode conversion from the elliptical surface wave into a longitudinal wave. But I now tend to think that the end result of all the intricate physics of the breaking mechanism is a conversion to a straightforward flow, analogous to DC. My earlier suggestion of using a diode to rectify an EM wave and produce this sort of action seems to have a similarity with a shallowing beach, where the bottom of the waves is curtailed, causing a sort of rectification effect.
"DC" action also seems to be involved when the waves are created. The heads of the waves stand up out of shelter and are pushed by the wind. They gain energy and grow. If they grow too fast they re-distribute energy by spilling down the face of the wave (which can never exceed a slope of 6:1 I believe), a fairly gentle action. So the generation process resembles a linear version of an impulse turbine, where the air flow hits the blades.

 

[Jamison Lahman]

In analogy to mathematics. It is much easier to obtain a derivative than to integrate. The analog is a "derivation" of a phenomenon

You should investigate numerical differentiation v. numerical quadrature.

 

[sophiecentaur]

Google NWFAQ. A very good read on shocks.

I 'Googled' and got a vast list of hits. If you could be a bit more specific then I could perhaps read what you are referring to.

 

[sophiecentaur]

The heads of the waves stand up out of shelter and are pushed by the wind.

Under some circumstances, yes but you do not need much wind at all for a wave to break. The wind can even be offshore. The effect of breaking is more to do with the bottom section slowing down than the top section accelerating.

 

[Jamison Lahman]

I 'Googled' and got a vast list of hits. If you could be a bit more specific then I could perhaps read what you are referring to.

Computational texts will do it far more justice than I can, but, to use my own term, differentition is 'flaky' with regard to the step-sized used. See attached images:

It is common for textbooks (especially old ones like Computational Physics by Koonin and Meredith from ~1970 and before symbolic computing from which the images are from) to highly discourage computational differentiation if possible.

Let me know if it is still unclear and I can maybe find a better explanation from text.

 

[sophiecentaur]

Let me know if it is still unclear and I can maybe find a better explanation from text.

Those numbers really don't help me at all. A bit of context about shock waves would be appropriate.

 

[Jamison Lahman]

Those numbers really don't help me at all. A bit of context about shock waves would be appropriate.

The behavior of the error (going from positive to negative is of interest here. Also the error for integration converges to 0 for much larger values of h).

This is a mild digression from shockwaves, but in direct reply to OP's statement in the quoted post.

 

[sophiecentaur]

OP's statement in the quoted post.

Which quoted post? You started off by quoting My Post, about shock waves being local but I was not the OP.
It would really help if you were a bit more fulsome with your writing. That last post still means very little to me (or many other readers, I fear).
Whilst you may know everything there is to know about this topic, if you want your ideas to be taken in by the readers of the thread, you need to help us a bit. We may not actually be thinking along your lines until you give more guidance.

 

[Jamison Lahman]

Which quoted post? You started off by quoting My Post, about shock waves being local but I was not the OP.
It would really help if you were a bit more fulsome with your writing. That last post still means very little to me (or many other readers, I fear).
Whilst you may know everything there is to know about this topic, if you want your ideas to be taken in by the readers of the thread, you need to help us a bit. We may not actually be thinking along your lines until you give more guidance.

The post I quoted in my initial comment. Specifically, comment #15 in the thread.

The reason I am not being completely fulsome is because it is a digression from the topic and one OP may not even be interested in.
Exerts from Computational Physics, Koonin and Meredith for context:

...

 

[sophiecentaur]

I really would appreciate you telling us how that apparently random cut and paste is relevant, either to the OP or to the topic of shock waves. Do you genuinely believe that it is a sequiter to any of the preceding posts?
Post #15 introduced Black Holes. Is that the link?
It's several months before April 1st.

 

[Jamison Lahman]

I really would appreciate you telling us how that apparently random cut and paste is relevant, either to the OP or to the topic of shock waves. Do you genuinely believe that it is a sequiter to any of the preceding posts?
Post #15 introduced Black Holes. Is that the link?
It's several months before April 1st.

It is directly relevant to the sentence quoted in my first post, as I have mentioned before. I genuinely can't clarify any more than that. I have also twice clarified it as a digression, yet you persisted I expand further. I genuinely don't know what more you want.

 

[sophiecentaur]

It is directly relevant to the sentence quoted in my first post,

Perhaps if you posted this as a new thread in the Mathematics Forum it may make more sense to more people.

 

[Jamison Lahman]

Perhaps if you posted this as a new thread in the Mathematics Forum it may make more sense to more people.

K.

 

[nikkkom]

I 'Googled' and got a vast list of hits. If you could be a bit more specific then I could perhaps read what you are referring to.

The very first hit:

http://nuclearweaponarchive.org/Nwfaq/Nfaq0.html

 

[jerromyjon]

The very first hit:

http://nuclearweaponarchive.org/Nwfaq/Nfaq0.html

It took a bit of searching to find this section:

3.6.1.1.1 Free Surface Release Waves in Gases

Let us assume that material supporting the shock wave is a gas. Since the pressure change in a rarefaction wave is always continuous (no instantaneous pressure drops), the pressure at the leading edge of the escaping gas is zero (in keeping with the requirement of equal pressures at the gas/vacuum interface) and the process of converting internal energy into kinetic energy is complete. The front edge thus immediately accelerates to the final maximum velocity (escape velocity) when it reaches the free surface. Farther back in the release wave the pressure increases and the velocity decreases. At the release wave boundary (which moves backward at c_s) the pressure and velocities are the same as in the original shock wave.

The escape velocity of a gas is equal to:

Eq. 3.6.1.1.1-1

u_escape = (2*c_s)/(gamma - 1)If we use a frame of reference in which the unshocked gas was stationary we get:

Eq. 3.6.1.1.1-2

u_escape = (2*c_s)/(gamma - 1) + u_particleand the rear edge of the release wave travels backwards at

Eq. 3.6.1.1.1-3

v_release = u_particle - c_sThe release wave thus stretches itself out with time at a speed of:

Eq. 3.6.1.1.1-4

((2/(gamma - 1)) + 1)*c_swhich for a perfect monatomic gas is 4*c_s.

It contradicts the concept of sound waves crashing summed in one sentence, "Since the pressure change in a rarefaction wave is always continuous (no instantaneous pressure drops), the pressure at the leading edge of the escaping gas is zero (in keeping with the requirement of equal pressures at the gas/vacuum interface)"

 

[nikkkom]

Rarefaction wave is not a shock wave, and can't become one.

You need section "3.4.3 Hydrodynamic Shock Waves"

 

[sophiecentaur]

The very first hit:

http://nuclearweaponarchive.org/Nwfaq/Nfaq0.html

Which particular phrase / sentence / paragraph should I read?
If you have a point to make then why not help the reader with where it is? Do you expect a casual contributor to top through the whole of that link and discover where your point is being demonstrated? Full marks to jerremyjon for finding it but should he have had to go to all that trouble? PF normally tries to be helpful, rather than to set people examination questions.
But it seems to confirm that this sort of thing doesn't happen in a free wave and must involve significant differences in the motion of parts of the medium.

 

[nikkkom]

Which particular phrase / sentence / paragraph should I read?
If you have a point to make then why not help the reader with where it is? Do you expect a casual contributor to top through the whole of that link and discover where your point is being demonstrated?

You need section "3.4.3 Hydrodynamic Shock Waves"

But I also strongly recommend reading the entire FAQ. You will increase your knowledge of nuclear weapons physics x100.

 

[jerromyjon]

You need section "3.4.3 Hydrodynamic Shock Waves"

3.4.3 Hydrodynamic Shock Waves

Compression waves are fundamentally unstable. They naturally tend to steepen in time and eventually (if they propagate long enough) will become infinitely steep: a shock wave. On the other hand, rarefaction waves are stable and a rarefaction shock (a sudden pressure drop) is impossible.

from:
3.4.1 Acoustic Waves
Any local pressure disturbance in a gas that is not too strong will be transmitted outward at the speed of sound.

 

[DarioC]

I can't think of anything for light yet, but perhaps for sound waves: Make a long bar consisting of layers of material that conduct sound at different velocities. If in fact that is a characteristic of different materials. Eg wood, plastic, metal. Then strike the bar on the end and then find some way to (visually?) observe the sound in transit or arriving at the other end of the bar. Guess I should research sound/shock velocities in different materials.
DC

 

[sophiecentaur]

You need section "3.4.3 Hydrodynamic Shock Waves"

But I also strongly recommend reading the entire FAQ. You will increase your knowledge of nuclear weapons physics x100.

Yes. I realize I am somewhat 'under-read' about a lot of topics - this is one of them. There must be a lot of people like me who have dipped into the thread and a bare reference to a long and difficult link is not going to encourage them to follow it. I always reckon that some personal input is worth while. A paragraph in one's own words, even when it's at a lower level than really necessary, is worth while, just to keep a thread going and to address a wider audience.

 

[sophiecentaur]

3.4.3 Hydrodynamic Shock Waves

Compression waves are fundamentally unstable. They naturally tend to steepen in time and eventually (if they propagate long enough) will become infinitely steep: a shock wave. On the other hand, rarefaction waves are stable and a rarefaction shock (a sudden pressure drop) is impossible.

from:
3.4.1 Acoustic Waves
Any local pressure disturbance in a gas that is not too strong will be transmitted outward at the speed of sound.
View attachment 210241

That picture made me realize that the surface wave that's set up when a boat is traveling at even a low speed, exhibits many of the characteristics of a breaking wave. The water at the top of the bow wave is traveling backwards, relative to the boat and the bow wave is continually 'breaking'. It makes me think that the equivalent must happen for other wave types but there is a very significant difference for water surface waves and that is they are very dispersive (speed is proportional to √λ - see link). You would need a very special medium for this with sound or EM, I think.