We have heard about the definition of a wave - disturbance in the matter or something. But can we think that light is a wave and so does it have vibrations (oscillations). Does it produce sound then? I am not talking about our audible range and consider it in our atmosphere only(material medium).
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4$\begingroup$ Sounds are vibrations in a material. Light waves are oscillating EM fields. Why would light produce sound? $\endgroup$– Pedro PinhoCommented Mar 2, 2021 at 4:26
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1$\begingroup$ Does light not have particle nature? It can produce sound that way! $\endgroup$– Prof. MeowCommented Mar 2, 2021 at 4:30
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1$\begingroup$ in some circumstances, it does. But again, why would that imply in light producing sound? $\endgroup$– Pedro PinhoCommented Mar 2, 2021 at 4:32
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1$\begingroup$ I think you are misunderstanding things. Photons and Phonons (quantized material oscillation) are completely different things. Light does not produce sound because it is not a vibration on a material. $\endgroup$– Pedro PinhoCommented Mar 2, 2021 at 4:36
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3$\begingroup$ Yes, photons can cause sound by local excitation of matter. And sound can make light via sonoluminescence, where high-energy sound causes cavitation bubbles which collapse with enough energy to give of light. Both processes are very roundabout ways of energy conversion. By similarly long roundabout route, light can make electricity, which can heat an element, which can fry an egg.This does not mean that light makes my breakfast! $\endgroup$– PcManCommented Mar 2, 2021 at 6:25
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6 Answers
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Sound is a vibration in a physical medium. Specifically a pressure wave in the molecules of matter.
Light is a vibration in the Electromagnetic Field, which manifests as discrete photons each possessing a specific frequency, and moving at a constant speed.
Sound does not, except very indirectly, make light.
Light does not, except very indirectly, make sound.
The two things are about as different as can be, despite both bearing similar tags of "vibration" and "wave" and "energy carrier".
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Certainly the atoms and molecules in objects around us are vibrating on a microscopic level and at their surfaces, those vibrations would induce vibrations in the air. But we don't hear anything because the amplitudes are so small. Thus they don't travel very far away from the surface.
These atoms and molecules are vibrating because all objects around us are at a temperature much higher than zero Kelvin. They are at these temperatures because heat is transferred to them from the air surrounding them by conduction and convection.
IR photons can excite vibration modes as well in certain materials - IR photons of the correct frequency will be absorbed by objects. So IR photons can excite vibration modes in solids. These again, would probably induce tiny motions in the air molecules directly at the surface of an object.
This is the only way I can think of where photons can indirectly produce a sound. They don't produce sound on their own because they don't have a physical medium that they create vibrations in - that is why they can travel in vacuum.
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$\begingroup$ Yes, certainly it can produce sound at a particular condition(s). That's why I was confused when the thought occurred in my mind. $\endgroup$ Commented Mar 5, 2021 at 2:42
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High power laser radiation can cause electric breakdown in the air, the breakdown produces sound. See, e.g., Applied Acoustics 65 (2004) 325–340.
Their abstract:
"When a high-power laser beam is focused at a point, the air at the focal point is heated to temperatures of thousands of degrees within several nanoseconds and breaks down. This generates a spark that, in turn, is accompanied by an acoustic shock wave. The acoustic shock waves generated by focussing the beam from a pulsed laser with a 1064 nm wavelength and a power of 800 mJ per pulse have been measured using 1/4″ and 1/8″ B&K microphones. Nonlinear sound levels are observed up to 1.5 m from the laser-induced sparks. Beyond a certain region close to the source, levels are found to decrease in a manner consistent with spherical spreading plus nonlinear hydrodynamic losses. Analysis of the waveforms shows that the acoustic pulses associated with the laser-induced sparks are more repeatable and have higher intensity than those from an electrical spark source. Laser-generated acoustic shock waves are ideal for simulating a blast wave or a sonic boom in the laboratory and for studying the associated propagation effects. To illustrate this application, the propagation of the laser generated shock waves over a series of different hard, rough surfaces has been investigated. The results show the distinctive influences of ground roughness on the propagation of the shock wave."
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$\begingroup$ The question asks about the light as wave, not laser! $\endgroup$ Commented Mar 2, 2021 at 4:57
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$\begingroup$ @Prof.Meow : It is the light from the laser that causes electric breakdown in the air. This light can be regarded as wave. $\endgroup$ Commented Mar 2, 2021 at 5:55
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$\begingroup$ haha you will soon find out light is both a wave and a ray :P @Prof.Meow $\endgroup$– BrianCommented Mar 4, 2021 at 21:24
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The frequencies of visible light do not correspond to those of audible sound.
Em waves with frequencies corresponding to those of audible sound can however produce sound when interacting with thin, easily vibrated objects;
This is thought to be one way that meteors produce sound in fact.
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$\begingroup$ As it’s currently written, your answer is unclear. Please edit to add additional details that will help others understand how this addresses the question asked. You can find more information on how to write good answers in the help center. $\endgroup$– Community BotCommented Jul 8 at 11:00
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Yes it does. Check Brillouin scattering (https://en.wikipedia.org/wiki/Brillouin_scattering). Here your light can scatter to produce acoustic waves in a medium. In a less precise setting, as was mentioned already if you take a powerful pulsed laser and send it through a focusing lens, you can create plasma in air which will be visible to a naked eye and will also buzz at the repetition rate of the laser pulse train. A very audible (and annoying) sound it is indeed.
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I assume that you mean to ask why ordinary light passing through air does not produce audible sound waves. It probably does as air molecules scatter light. However the scattering effect is very weak, fortunately, or we would live in a blur, and it would produce very high frequency noise as it impacts individual molecules. These are at roughly 3 nm apart so this theoretical noise would center at a frequency about 10$^11$ Hz. The dissipation of such high frequencies is perhaps a nanosecond, because the mean time between collisions is 0.2 ns. You will have a hard time detecting this effect but with a properly designed experiment it could be possible. Thinking very cold dense air and high laser intensity ...
