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B Are light waves/ EM waves damped?

  1. Feb 4, 2017 #1
    We can't see objects from objects far away from us. Why? I think light waves damps! When it reaches our eyes it's amplitude is too small to be visualised! Is this true? If indeed EM waves are damped then why? If not please give a suitable definition for the mentioned phenomena too !
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  3. Feb 4, 2017 #2


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    Light travelling through empty space does not lose strength (although it does spread out). The wikipedia article on "tired light" is a good start.
    Last edited: Feb 4, 2017
  4. Feb 4, 2017 #3


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    It is not damped. It is because the energy gets spread out over a wider area that the amplitude becomes small (in QM terms, the number of photons per unit area becomes smaller) as it goes further from the source. Why do you think a light bulb is harder to look at with your eyes when you are an inch away, versus when you are 100 meters away?

    If you have a plane wave, collimated light source, such as a laser, then the intensity or brightness can be preserved over longer distances, and it will be as bright 1 inch away as well as 100 meters away. This, this is easily an indication that there is no intrinsic damping.

  5. Feb 4, 2017 #4
    Thanks ZZ I got your point At least for now this much will help me to progress
    Last edited by a moderator: Feb 4, 2017
  6. Feb 5, 2017 #5


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    You can work out what fraction of the light from a star reaches your eye. It's the area of your pupil divided by the area of a sphere with a radius equal to the distance to the star. It's a wonder any photons make it.
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