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B Light shot up to the sky

  1. Jun 17, 2016 #1
    If I shot/flash lights up to the sky, will the lights or photons fly up to the sky then to the space then to the top of the universe?? Will it stop?
     
  2. jcsd
  3. Jun 17, 2016 #2

    Nugatory

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    Staff: Mentor

    The light will travel until one of two things happens to it: Either it will be absorbed because space is not completely empty, or it will spread out until it becomes too weak to detect. That's assuming that it makes it past the atmosphere of the earth, which it won't on a cloudy day.
     
  4. Jun 17, 2016 #3
    And the effect of the clouds is to scatter the light.
     
  5. Jun 17, 2016 #4

    Vanadium 50

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    And the universe doesn't have a top.
     
  6. Jun 18, 2016 #5
    Thanks for your answers.
    One more question..
    If I flash the light onto the wall which is far from myself, why does the light become weak or even disappear?? But, if the wall is near, why does the light become strong?
    What absorbs the light in its travel to the wall?
     
  7. Jun 18, 2016 #6

    davenn

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    as nurgatory said in as earlier answer, it spreads out
    like this ......

    inverse_square_law.jpg



    Dave
     
  8. Jun 18, 2016 #7
    What determines how "strong" the light is, to use your term, is how much light falls on a given area on the wall. As davenn showed, the further you put the wall, the more the light has spread so the amount of light per unit area is less compared to when the wall is closer, so it doesn't look as strong.
     
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