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Is it possible to use sound to change the wavelength of light, and therefore its perceived color?

In an effort to rephrase my question from the information gained in the first answer, would it then be possible to use sound to change the density of open air so that the light passing through it would be affected drastically enough to change the color?

enter image description here

Jordan
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An acousto-optic modulator sends an acoustic (sound) wave with frequency $\nu_s$ through a crystal, forming a moving diffraction grating something like the illustration you provided. Sending a laser beam with frequency $\nu_l$ through the grating results in multiple diffraction orders, with shifted frequency $\nu_l +n\nu_s$, where n is the diffraction order number.

So yes, it's possible to shift the frequency of light using sound.

However, acoustic frequencies, even in an acousto-optic modulator, are much lower than laser frequencies. Green light at 540 nm has a frequency of about 560 x $10^{12}$ Hz, while the fastest A-O modulator use an acoustic frequency of about 1 x $10^9$ Hz. That means an A-O modulator can change the frequency of green light by at most a few parts in 560,000. The human eye can distinguish light frequency differences as color differences, at best on the order of 2 parts in 500. So, an A-O modulator would need to use an acoustic frequency about 1000 time higher than is currently possible, in order to shift visible light frequencies enough to be perceived by human vision. It would be hard to call such a high frequency "acoustic"!

S. McGrew
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  • Light changes frequency, i.e the hnu of its photons, when doppler shifted, so I guess it is something like this, changes in inertial frames. I will correct my answer. – anna v Jan 30 '19 at 16:34
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To start with, sound is "seen" by light reflection whenever a mirror or glass vibrates, the images vibrate.

Visible light frequencies are measured in teraHerz, sound goes up the 20.000 Herz for supersonic. The frequency of light is fixed in a fixed inertial frame. ( see the answer by S.McGrew for a "moving diffraction grating"). What can change easily is color perception, i.e. how our eyes detect color.

Light could be diffracted in the image you provide, there exists a paper from 1935 , on the diffraction of light by sound-waves of high frequency in a medium, discovered by Debye and Sears and Lucas and Biquard,

and another in 1954

It is not a very active field. I think because of the large difference in the range of frequencies of sound and light what you propose is not possible even for color perception.

On the other hand, I would guess, using reflections through layers of colored glasses vibrating at a given sound frequency might change the mix of primary frequencies and thus change the perception of the color tuned to the sound frequency.

anna v
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The frequency of the reflections off of any object are shifted up and down slightly as it moves towards or away from you. A radar system would be able to identify these Doppler shifts in the reflections from an oscillating speaker diaphragm, although it would not be perceptible.

Display Name
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at first glance it seems possible to change the color (but not the wavelength) considering the following points:

  • denser air has a different refractive index
  • a given light color can be obtained with a mix of other colors
  • different wavelengths react differently when refracting like in the atmosphere
  • different polarizations of light are reflected in different amounts when encountering a change in refractive index

So a mix of colors (for ex white light) or better a mix of colors with each having a different polarization should change when passing through sound waves. If you want air lensing, the sound wave pattern shoulnt be parallel as pictured (a sheet of glass has parallel walls and doesnt do lensing) but you still can get the polarized reflection.

Schlieren imaging should provide further interesting examples.

Manu de Hanoi
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