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Can particles be frozen/stopped and studied?

  1. Oct 17, 2011 #1
    Hi guys and girls. This is my first post. I am a college student, science enthusiast, but layman still. So I thought it would be appropriate for my first post to be a question (since I have way more of them than answers in this realm)
    I've read about light being slowed down, i.e http://news.bbc.co.uk/2/hi/science/nature/1124540.stm" [Broken]

    And I've read that light has both properties of waves and particles. It is my understanding that photons are always moving in the natural world, in fact all particles are constantly moving. Stop me if I'm wrong here, I am a layman. So my question is whether or not we could freeze, trap, or suspend a particle in a way that it is essentially stationary relative to us while still retaining its normal properties? If we can completely stop light we would have to see it as either a particle or a wave, not both, correct? If possible, could we somehow mechanically dissect a particle in way biologists do and remove each of its constituent subatomic particles for study? Even if this is possible, would it tell us anything about these particles we don't already know?

    I know I presented a lot of questions, some of which might be goofy to the experts around here, but I'd like some feedback regardless, thanks.
     
    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Oct 17, 2011 #2
    Welcome to Physics Forums!

    Light cannot be stopped, trapped, or slowed down (aside from normal refraction). Articles written for the layman, like the one you linked to, that claim light has been frozen are purposefully written in a misleading way to seem more interesting to the uninformed reader. "Freezing light" experiments do not actually trap light. Rather, the light beam's shape is stored in a block of matter. The light itself is gone, but the information it carried is stored and can be retrieved. There is not much more interesting going on in these type of experiments than when a camera "freezes" the light coming from your face and produces an image of your face. Light always travels at speed c in vacuum.

    Now matter is a different case. We can stop, freeze, and trap matter to study it. Some of the most interesting fields that touch on this involve: http://en.wikipedia.org/wiki/Bose%E2%80%93Einstein_condensate" [Broken].
     
    Last edited by a moderator: May 5, 2017
  4. Oct 17, 2011 #3
    Thank you for your response chris. I am confused about the meaning of your statement, "The light itself is gone, but the information it carried is stored and can be retrieved."

    By "information" do you mean the physical properties of the light, i.e color and wavelength or are you saying light can literally store information as we know it, like say a word document?

    The way you described it brought visions to my mind of "fossilized light," if that makes any sense.

    Furthermore, am I correct in assuming that you are saying that particles that have mass can be trapped and studied in a way like, or similar, to how I described?
     
  5. Oct 17, 2011 #4
    It was my impression that light can be slowed, depending on the medium it is traveling through?
     
  6. Oct 17, 2011 #5
    That is how I interpret it as well.
     
  7. Oct 17, 2011 #6
    And looking at wikipedia, this is what it claims as well. Upon thinking about it, I realized that the change in the speed of light is what gives rise to snell's law, or the refracting of light when the medium the light is traveling through changes.

    I would have to see a source claiming that the speed doesnt change, just the ability to access information.
     
  8. Oct 17, 2011 #7

    DaveC426913

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    Light always travels at c. When moving through a medium, it takes a non-zero time to get absorbed and re-emitted, which is what slows its progress through the medium. However, the light itself is always travelling at c.
     
  9. Oct 17, 2011 #8
    And this is caused by the atoms in the medium? Is it possible to pick a particular frequency which would cause the light to travel straight through a medium, without any absorption?
     
  10. Oct 17, 2011 #9

    DaveC426913

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    If you could find a medium that has no atoms...
     
  11. Oct 17, 2011 #10
    Do atoms absorb and re emit photons which do not match an energy level? If I remember right the photon will kick the electron up, but because it does not reach (or goes over) the energy level it will go back down to the original state and re emit the photon.
     
  12. Oct 17, 2011 #11

    DaveC426913

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    If the medium were to not absorb and re-emit the photons, it would also have a refractive index of one. There's only one circumstance that has a refractive index of one.
     
  13. Oct 18, 2011 #12
    Yes. Every time you email a Word document from your smartphone, you are sending a beam of light (not visible light, but electromagnetic waves just the same) from your phone through the air to a cell phone tower containing the document's information in the light's shape. The information is encoded in the wave's shape. When the cell phone tower receives the Word document, it converts the light shape to an electrical signal of the same shape. The electrical signal can then go to someone else's computer and show up on their screen. In this sense, the light signal is "frozen" even though the actual light wave itself is long gone. I don't personally like this terminology myself as it can be misleading, but the popular media seems to like to use this language to make the science seem exciting.

    The closest thing we have to light itself actually being frozen would be standing waves, such as in a laser cavity. The actually photons are still traveling at speed c, but the overall wave shape (called the mode pattern) seems to be frozen in the cavity.
     
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