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Shining Light - The Physics Behind This Phenomenon?

  1. Jan 7, 2008 #1
    I've taken a picture of my christmas lights. I'm wondering if someone could help me explain, or at least name, the phenomenon?

    http://img142.imageshack.us/img142/5925/physicsphotocontestto9.jpg [Broken]

    Why does light appear to come from 4 distinct points around the light? Even though some bulbs are rotated, the position of these 4 points do not rotate with it. It's always -up-, -right-, -left-, and -down-. Why?

    If someone could link me to an article about this phenomenon, or at least give me a name of it, that would help a lot. Some of my friends are saying it has to do with spherical aberration. But I don't understand how. It seems, to me, to be spherical aberration and the following pattern at the same time:

    http://img244.imageshack.us/img244/6599/physicsphotoexplainty7.png [Broken]

    Which could be caused by refraction, right? But how?

    Thanks for any replies.
    - Sane
    Last edited by a moderator: May 3, 2017
  2. jcsd
  3. Jan 7, 2008 #2


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    what happens when you rotate the camera?

    It could be diffraction or saturation of the detector array.
  4. Jan 7, 2008 #3
    It's always up with respect to the orientation of the camera. I took another picture to clarify:

    http://img142.imageshack.us/img142/9733/physicsphotorotatekn4.jpg [Broken]

    So I guess that means it has to do with the lens inside the camera. Is there anything specific I can research?
    Last edited by a moderator: May 3, 2017
  5. Jan 7, 2008 #4


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    Staff: Mentor

  6. Jan 7, 2008 #5
    Diffraction spikes, brilliant! Thanks. I get many excellent hits with this term.

  7. Jan 7, 2008 #6
    Do eyelashes cause a similar phenomenon? How about the iris of a camera?
  8. Jan 7, 2008 #7
    It seems like it'll be anything that obstructs light directly before entering the lens. You can even place strings in front of a telescope and get diffraction spikes (as russ_watters has apparently done).
  9. Jan 7, 2008 #8
    I could not find an objective explanation of Diffraction Spikes anywhere... not even on Wikipedia. Most sites just referenced little things you could do, and the overall effect. I found a couple sites that explained very briefly what happens, so I tried to piece together all of these things to make the following analysis of my photo.

    (Disclaimer: This may not be 100% accurate, but if it helps anyone else who stumbles upon this thread get a better understanding of Diffraction Spikes, then great. And maybe someone could help correct any inaccuracies/elaborate on my analysis.)

  10. Jan 8, 2008 #9
    i don't understand how a solid object can bend light... i thought you need strong gravity to do that, as in huge stars in space? Shouldn't you just get a shadow star or something...
  11. Jan 8, 2008 #10
    That's one thing I wasn't clear on myself, and need to explain better once I understand it more. I don't think it's so much that it's bending it, but that the waves can go around obstacles. And that results in interference. Similar to the Double Slit Experiment. I think... Clarification, anyone?
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