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How intimate are the rays of light?

  1. Dec 5, 2011 #1
    1. Is there any clue as to how close two adjacent photons, coming from a distant star, in neighbouring paths, can be to each other?

    2. Do their paths make a minute angle? or coming from a distance and heading towards earth, they are dead parallel to each other?

    3. What, if the source of light is a distant powerful tiny mass, approaching a point in size? Shall we still be able to see parallel rays of light?
    Last edited: Dec 5, 2011
  2. jcsd
  3. Dec 5, 2011 #2


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    The rays coming from our own sun are usually considered to be parallel, and the sun is not that far away considering the distance to other stars. But as you know the sun does take up certain arc in the sky, so a ray from the left side is not exactly parrallel to one coming from the right side.

    For star light, since a star is light years away, that angle becomes smaller and smaller as you observe a star farther and farther away. Most stars look like point sources of light so the rays would be very very parallel.
  4. Dec 5, 2011 #3
    Isn't that the case that as a source of light shrinks to a point, the emission of light resembles the radii of a sphere?
  5. Dec 5, 2011 #4


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    They can occupy the same location as photons are Bosons.

    Depends on what you mean. When forming an image only light rays that are approximately parallel are used in a telescope. The actual light from the star shines in all possible directions and angles though.

    Yes. That is how we view stars in most telescopes currently. They are so far away that they are very nearly a point source.
  6. Dec 6, 2011 #5

    What you have mentioned is quite respectable but what I have in mind, when I say a point source is, actually, not a distant giant star (which is only a point from a distance) but something in order of, for example, and electron emitting powerful light enough to reach us from a long distance .As it gets farther and farther, the rays of its light become more and more scarce (because of their divergence).
    The question is when will it come the point that you can only have one ray of light, say, in your telescope. It’s that happens there is an evidence (theoretically) that the reason we have parallel rays of light is that they are coming from an expanded surface.
  7. Dec 6, 2011 #6


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    Each "spot" on an image has been emitted from the same "spot" on the object. They are only parallel because of the great distance between us and the object allow us to consider them parallel even though they are only approximately parallel in reality.
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