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Light OR Sound

  1. Aug 15, 2009 #1
    Light OR Sound!!!

    When we clap, we hear a sound..The reason is that on clapping sound waves are produced....
    My question here is why???
    Why Does Clapping produce a sound wave and not a light wave...Or when we light a torch, why are sound waves not produced...
    Also, When a electron jumps from conduction band to the valence band, light is produced...What is the reason for this...
    How do we decide by our intution whether light or sound would be produced...
  2. jcsd
  3. Aug 15, 2009 #2


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    Re: Light OR Sound!!!

    Sound is produced by the vibration of the molecules of a medium, such as air. So clapping your hands creates a pressure wave which propagates and we experience this in sound. As you appear to know, photons are emitted from energy state transitions. The jumping electron, in the case you mentioned, releases a photon because it moves from a higher to a lower energy state, and the conservation of energy states that the extra energy must go somewhere, so it is released in the form of a photon.

    In sum, light is a quantum mechanical property while sound is macroscopic.
  4. Aug 15, 2009 #3


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    Re: Light OR Sound!!!

    Lighting a torch most certainly does produce sound. They are entirely separate processes which are not mutually exclusive.
  5. Aug 15, 2009 #4
    Re: Light OR Sound!!!

    We don't rely soley on intuition because your "intuition" and mine are likely quite different. Also your visual acuity and hearing might be quite different and could affect your perception of what's going on. Actual production sound vs light of course is a different matter.

    But by having a basic idea of the physical processes involved in the production of each, described above, you can make some informed guesses about, for example, slapping an oar on water; bubbles emerging in boiling water, radium decay, observing effects of a thunderstorm.
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