Can sound use light as a medium to pass through?

In summary: But at the smallest level, this distinction becomes less clear.The mass energy of light is not practical to use in an everyday sense for measuring mass.In summary, the conversation discussed the possibility of using light as a medium for sound transmission based on its density. However, it was concluded that this is not possible as sound requires a medium with mass and mechanical properties, while light consists of massless photons. The concept of the Casimir effect was discussed, which involves a force between uncharged plates in a vacuum, but it was noted that this effect is not technologically useful for sound transmission. The conversation also touched on the definitions of sound and light, and the relationship between mass and energy. Ultimately, it was determined
  • #1
winchy
5
0
ok, ill try to explain myself as best as i can. you have a box with all walls with "perfect mirrors", remove all air, then force light into the box. assuming no light escapes would the "density" become great enough for sound to use the light as a medium to travell through. i hope explained myself well enough and hope someone might help me with this problem.
Thanks
 
Science news on Phys.org
  • #2
No, to carry sound a medium needs to be able to pass along vibrations from one atom/molecule to the next.
Photons do not affect other nearby photons (except in some self focussing effects of very high power lasers).
 
  • #3
I'm not sure that this is impossible. I'm going to speculate along these lines. In the casimir effect, there is a force between uncharged plates in the "vacuum". The casimir force is due to the fact that the available states of an electromagnetic field between the plates is discrete due to boundary conditions, compared to the field outside the plates. So that would be a photon field between the plates. Since there is a force between the plates, then moving one plate mechanically (counting any mechanical movement as sound) would be transmitted to the other plate. In this way, perhaps photons could transmit sound?
 
  • #4
There's another way, but it's pretty stupid. If I blast a high intensity laser at your ear drum, I could probably pop it. And you might hear the popping.
 
  • #5
atyy said:
I'm not sure that this is impossible. I'm going to speculate along these lines. In the casimir effect, there is a force between uncharged plates in the "vacuum". The casimir force is due to the fact that the available states of an electromagnetic field between the plates is discrete due to boundary conditions, compared to the field outside the plates. So that would be a photon field between the plates. Since there is a force between the plates, then moving one plate mechanically (counting any mechanical movement as sound) would be transmitted to the other plate. In this way, perhaps photons could transmit sound?

What you are describing amounts to modulating the light by vibrating the source (mirror). This is quite another matter! Of course, modulated light waves can carry sound information. However, the OP was asking about using light as a medium for the transmission of sound based upon the density of the light. That is not possible as sound requires a medium which can pass a mechanical wave, which means the medium must contain something mechanical such as atoms or molecules. Light consists of massless photons only, no atoms or molecules so it cannot pass a mechanical wave regardless of how “dense” or intense the light.
 
  • #6
atyy said:
There's another way, but it's pretty stupid. If I blast a high intensity laser at your ear drum, I could probably pop it. And you might hear the popping.

Well, I agree with the first sentence, at least. :rolleyes:
 
  • #7
Your not hearing anything from the light itself, just the sound of your eardrum popping.

In order for a median to carry sound, it needs to have mass and be affected by electromagnetic atomic forces. I'm pretty sure light doesn't have either of those qualities not to mention its always traveling a lot faster than the speed of sound.
 
  • #8
Simply put, light is not a medium.
 
  • #9
schroder said:
What you are describing amounts to modulating the light by vibrating the source (mirror). This is quite another matter!

russ_watters said:
Simply put, light is not a medium.

I think the casimir effect would be a bit different from the usual way of changing sound into electricity. The most common way is to use a microphone, in which sound essentially vibrates the charged plates of a capacitor. The casimir effect is a bit different since it involves uncharged plates. Of course the effect is extremely delicate, and requires our best precision to detect it, so it's not anywhere close to being technologically useful for a microphone now (though the nanotech guys may find it important).

But I think it's mostly semantic. Like whether a current can pass through a capacitor. In classical electromagnetism, no, by the *definition* of current - we say it changes into a "displacement current".

It's interesting that there is an accepted way of saying that a current passes through a capacitor - within the approximation of circuit theory, for alternating current.
 
  • #10
schroder said:
What you are describing amounts to modulating the light by vibrating the source (mirror). This is quite another matter!

russ_watters said:
Simply put, light is not a medium.

OK, I get how this is not just semantic. If I put my ear in the box of photons, I would not hear anything, no matter how hard the mirror was vibrated. In principle it is possible if an artificial ear was used, but because of the limits of sensitivity on my hearing, we will need to up the photon density to the point where I'd probably vaporise my ear first!

So it is semantic! There are two definitions of sound - one is mechanical and physicky. The other is biological and perceptually. In the first, sound is just another type of energy, and the ability to convert between different forms of energy is a fundamental idea in physics - there is no well-defined sub-discipline of physics called "mechanics" that is distinct from "electromagnetism". To make a clear distinction between sound and light, we need biology.
 
  • #11
but light has a mass, 2kg of light falls on the Earth everyday. and isn't light and mass the same thing, that's why E=mc2. mass energy..?
 
  • #12
winchy said:
but light has a mass, 2kg of light falls on the Earth everyday. and isn't light and mass the same thing, that's why E=mc2. mass energy..?

Yes. The very strictly correct answer is yes. Sound is defined as a mechanical oscillation. Light is an electromagnetic oscillation. But strictly speaking, we don't know where mechanics ends and electromagnetism begins.

In everyday physics, we can distinguish between mechanics and electromagnetism, so in that sense, the answer is no.
 
  • #13
ok, so in a perfect and toally therical world it could happen?
 
  • #14
winchy said:
ok, so in a perfect and toally therical world it could happen?

Yes!

schroder said:
What you are describing amounts to modulating the light by vibrating the source (mirror). This is quite another matter!

The difference in opinion between schroder and me comes down to a matter of definitions. That sound can be turned into light is not contested - it's called radio broadcasting. The one technicality is whether we allow the walls of the box to be charged or not. In radio, and all technologically common ways to turn sound into light, the walls have to be charged. There is an effect called the casimir effect ("the friction of vacuum"), where the walls don't have to be charged. It is an extremely delicate effect, long predicted, but only recently measured.

The way you are approaching it, from E=mc2 is a useful heuristic. But even without that, just from classical physics, we can say that light has momentum. That is where the division between mechanics and electromagnetism begins to disappear. The equations of classical physics that say this are Maxwell's equations, and they led logically (with lots of help from experiments!) to the relativistic notion of mass-energy equivalence you started from.
 
Last edited:
  • #15
No, no, no. Light does not have mass like ordinary objects do. When someone says that mass is lost as light by the sun, it is converted from matter to energy. That's what the equation is talking about. It doesn't mean that energy and mass are the same thing, just that you can transform one into the other.

And the casimir effect isn't the same thing as using the light as a medium - and that's even assuming it would work at all. The casimir effect is an extremely weak force and acts over a very short distance.

The wording of the op is pretty specific: "Can sound use light as a medium to pass through?" The answer is quite simply no. Light is not a medium and it cannot transmit sound the way a medium (ie, air, water, steel) transmits sound.
 
  • #16
well i thank you all for your help. now to learn more and ponder some.
 

What is the concept of using sound to pass through light?

The concept of using sound to pass through light is known as acoustic cloaking. It involves manipulating the properties of sound waves to make them invisible to light waves, allowing them to travel through transparent materials without being detected.

How does sound interact with light when passing through a medium?

When sound waves travel through a medium, they cause the molecules in the medium to vibrate. This vibration can create small changes in the density of the medium, which can in turn affect the way light travels through it. By manipulating these changes in density, scientists can control how sound and light interact in a medium.

What are the potential applications of using sound to pass through light?

The potential applications of acoustic cloaking are varied and far-reaching. It could be used to create invisible barriers or shields, to improve medical imaging techniques, or to enhance the performance of optical devices such as telescopes and microscopes.

Is acoustic cloaking a new concept?

No, the concept of using sound to pass through light has been around for several decades. However, recent advancements in technology and materials have made it more feasible and practical to achieve in real-world applications.

What are the challenges in implementing acoustic cloaking?

One of the main challenges in implementing acoustic cloaking is finding the right materials that can effectively manipulate sound waves without affecting the properties of light. Additionally, there are still limitations in terms of the size and complexity of objects that can be cloaked, as well as the energy requirements and costs involved in the process.

Similar threads

Replies
30
Views
9K
Replies
9
Views
2K
Replies
3
Views
1K
Replies
8
Views
1K
Replies
10
Views
2K
Replies
19
Views
18K
Replies
8
Views
2K
Replies
30
Views
561
  • Special and General Relativity
Replies
22
Views
1K
Back
Top