Can Electromagnetic Radiation Create Sound?

In summary, the conversation discusses the possibility of electromagnetic radiation, such as light, being able to trigger the sensation of sound through momentum transfer. However, it is determined that sound is a macroscopic phenomenon that requires a population of molecules to create compressions and rarefactions, and that light can only indirectly cause sound through mechanical effects. The conversation also mentions the use of photomechanical effects in medical applications and the concept of entropy in relation to the perception of sound.
  • #1
bockerse
23
0
Something I've been thinking about, and I just have no idea in which forum to post it. If the sensation of sound is due to the collisions of molecules against your eardrum, and they impart momentum transduced across your eardrum into phonons which occur in 'solids' as modes of vibration treated as bosonic particles that also have momentum, then could electromagnetic radiation of sufficient intensity and hi-frequency impart enough momentum to trigger sensation of sound? Is it really all due to momentum? My own smart-ass reply is: "Yes, it's called sight", but of course I mean literally sound. And what would light sound like?

Gerrit
 
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  • #2
Sound is a longditudinal wave i.e. compressions and decompressions in the direction of motion. Sound is not caused by the collision of molecules against your eardrum. Your eardrum can interpret certain frequencies of the londitudial waves of compressions; caused by some mechanical movement.

So in this sence, as light is a transverse wave (oscillations are perpedicular to direction of motion) and the oscillations are electromagnetic, your ear could not interpret EM waves as sound.

However, light is dicretely packaged as photons which carry momentum and as such a momentum transfer bewteen, say, a solid surface and light can and does occur(I know little about this)
. But again, any sound which arises from this would be due to the mechanical movement of the target medium producing compressions in the air etc etc, so the sound is not a direct result of the light.

Photomechanical effects are used also in medical application to break up kidney stones and other things by using short pulsed lasers to rapidly vapourise tissue causing shockwaves (at certain pulse durations).

But to answer your question, light can only give rise to mechanical effect which can cause sound (vibrations); and cannot dirrectly induce a sound, only secondarily.
 
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  • #3
Sound

I know that's the classical description of a sound wave in air. This is what all the engineers and physicists say. So would that then mean "sound" is purely a macroscopic phenomenon (not the perception of sound, but the 'essence' of sound)? An example of such a macroscopic-only phenomenon is entropy. If you view a molecular collision it appears reversible in time, and only when viewed on a 'large' scale is entropy apparent. So, would a single molecule or couple molecules bouncing around a box be entirely soundless because there is no way to model rarefaction and compression as with a population of molecules? I ask this because the longitudinal 'waves' produced by atmospheric pressure differentials ultimately do cause molecules to pelt your eardrum which triggers the sensation of noise (this is why we hear 'wind'). My suspicion was that even when considering a molecule or 2, the impulse of collision would be sufficient to produce phonons (if momentum was high enough). Hence, momentum would be what to consider and that opens the question to light which though massless, has momentum.
 
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  • #4
Light does exert pressure, and by modulating the intensity of the light you could in effect cause a transducer to think that sound was impinging on it. I have a feeling that the intensities needed would cook your eardrum, but maybe this has other applications.
 

1. What is the definition of sound?

Sound is a form of energy that is created by vibrations and travels through a medium, such as air or water, to be heard by our ears.

2. How do vibrations create sound?

Vibrations occur when an object is disturbed from its resting position, causing it to move back and forth rapidly. This movement creates waves of pressure that travel through the medium, which our ears interpret as sound.

3. Is sound all due to momentum?

No, sound is not solely due to momentum. While momentum is involved in the creation of sound, it is not the only factor. Other factors such as frequency, amplitude, and the characteristics of the medium also play a role in the production of sound.

4. How does the medium affect the speed of sound?

The speed of sound varies depending on the medium it travels through. Sound travels faster in denser mediums, such as solids, and slower in less dense mediums, such as gases. This is because the particles in a denser medium are closer together, allowing sound waves to travel more quickly through them.

5. Can sound travel through a vacuum?

No, sound cannot travel through a vacuum as there is no medium for the waves to travel through. This is why sound cannot be heard in outer space, where there is mostly a vacuum.

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