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Momentum of light

  1. Mar 28, 2010 #1
    I've read somewhere that only red light is used in photography because of its low energy which does not affect the photographic plate.
    So my question is that when light shines on a surface, is momentum transferred to the metal surface?
  2. jcsd
  3. Mar 28, 2010 #2

    Filip Larsen

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    Yes, any surface that reflects, absorbs or emits light will effectively act as if light imparted a very small pressure on it. Reflection, which can be thought of as an absorption followed by an emission more or less back the same way, gives up to twice the pressure. Light (including heat from black-body radiation) emitted from the "the other side" of the surface will of course reduce the effective pressure.

    You can look up how solar sails work to see a "practical" application of this effect.
  4. Mar 28, 2010 #3
  5. Mar 28, 2010 #4

    Char. Limit

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    Wavelength is inversely proportional to energy, or something like that.

    As an extension of the topic "momentum of light", if you shine light on an object in space, will the object start moving?
  6. Mar 28, 2010 #5


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    Staff: Mentor

    Solar Sail
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