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General Science => General Science => Topic started by: Karishma Bhoolia on 12/02/2009 13:30:02

Title: Can sound waves be turned into light?
Post by: Karishma Bhoolia on 12/02/2009 13:30:02

Karishma Bhoolia  asked the Naked Scientists:
   
Hi Chris

I was sitting in a yoga class recently when the instructor informed us all of how sound waves can be turned into colours.  She claimed if a piano keyboard could be extended by 31 octaves it would eventually begin playing the colour red.

I have a vague understanding that light and sound are completely different.  Sound waves being compression waves whereas light is a wave-like particle.  It is light of this distinction that I am completely baffled.  Is it either a theoretical or practical possiblity for sound waves to be turned into light?

If this is possible how would it work? Would we really have pianos streaming the colours of the rainbow?

I am almost immobilsed by confusion and your insight would be a welcome relief.

Regards

Karishma Bhoolia
South Africa

What do you think?

Title: Can sound waves be turned into light?
Post by: LeeE on 12/02/2009 17:16:01

You are correct Karishma, the two types of wave are completely different, and along the lines you suggest.

Title: Can sound waves be turned into light?
Post by: Soul Surfer on 12/02/2009 18:55:55

That may be true but there is an interesting phenomenon called Sonoluminescence where the energy from sound is converted into light by extremely non linear processes.

If you focus high intensity sound waves in a liquid to create an area where there is an extremely high intensity of sound.  This is best done at ultrasonic frequencies.

The extreme intensity of the sound causes the liquid to cavitate.  That is during the low pressure phase of the sound wave small bubbles form which then collapse when the high pressure phase is reached these bubbles collapse symmetrically to produce an extremely high concentration of energy this produces flashes of light look up sonoluminescence for more detail.  The energy density can even produce ultra violet and x rays.
It has also been suggested that this process could produce cold fusion but that is rather dubious.

Title: Can sound waves be turned into light?
Post by: daveshorts on 12/02/2009 19:07:57

Sonoluminescence does make light, but of a completely different frequency to the sound which you put in.

If you somehow created sound at 10¹⁴Hz (I think this is the rough frequency of visible light) then you would be vibrating charged things (mostly electrons) and if you vibrate charged objects they give off electromagnetic radiation, and  in this case of a visible frequency -> it would give off light.

This is however not to say that light and sound are at all the same thing. One is a vibration in a substance, the other is a vibration in the electric and magnetic fields.

Title: Can sound waves be turned into light?
Post by: techmind on 13/02/2009 16:13:03

Here's a link to a sonoluminescence experiment I set up:
  http://www.techmind.org/sl/


Back to the original question, yes light is electromagnetic wave rather than compression wave.
Visible light spans wavelengths of around 750nm (very deep red) to 350nm (near-UV). Green, in the middle, to which the eye is most sensitive has a wavelength of 555nm, which from f=c/wavelength gives a frequency of 5.4x10^14Hz ... so actually you need to go more like 40 octaves about audio anyway!