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What happens to the remainder of the energy

  1. Jan 23, 2005 #1
    I'm not really sure about such things, but this is my question. :smile:

    Say a photon of white light in incident on an object which is instrinically a blue object, just any regular blue object. Now (naturally) you see light (a photon corresponding with a wavelength that matches the blue region) that is blue. Does the incident photon energies an electron in an atom of the object, and upon return to its previous electronic state, a photon with wavelength corresponding with the blue colour is emitted...right?!

    What happens to the remainder of the energy... I mean in physics i was always taught that the object would "absorb" the other colours and release only the one corresponding to the colour of the object..does this 'light as a particle' theory explain this and account for the energy remainder.

  2. jcsd
  3. Jan 23, 2005 #2
    First of all, a single photon cannot be "white". "White" inherently assumes that you have many photons of varying wavelengths.

    When light is incident upon matter, it can do 3 things :

    - Transmit (specular or scattered)
    - Reflect (specular or scattered)
    - Get absorbed

    When absorption takes place, the photon energy can be used to produce more photons of lesser energy, or for deformation of the atomic structure. Deformation can be permanent (ex.: chemical reaction) or perhaps more commonly temporary (ex.: matter vibrations = phonons).

    Light particles are evidenced by the fact that absorption spectra can contain peaks of absorption. Such peaks correspond to wavelengths that are preferentially absorbed, and they are related to specific atomic or molecular transitions.
  4. Jan 23, 2005 #3


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    There is no such thing as a "white" photon. White is a superposition of photons across the entire visible spectrum.

    All incident photons are either adsorbed by the electron structure or transmitted through the material. The decay path of the electrons excited by the incident photons determines the color of the object.
  5. Jan 24, 2005 #4
    Thanks...I knew that "white light" was a superposition of the visible spectrum of light (in e-m theory) but I know little 'light-as-a-particle' theory, apart from that of the photo-electric effect.

    Thanks though, answered my question brilliantly.

    All the best guys! :biggrin: :biggrin:
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