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Thread: light beam

  1. #1 light beam 
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    optics question:

    1) how long can the shortest possible beam of light (not light-wave) be in the visible spectrum?

    2) how short a light-beam can our current technology produce?

    explanation too plz


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  3. #2  
    Universal Mind John Galt's Avatar
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    I don't think I understand the question. You do not want the shortest wavelength? Is that correct?
    You just want the light to travel a very short distance? Is that correct?


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  4. #3  
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    eek no ophiolite
    i do not want teh shortest wavelengt (correct) - but i want to know how short the shortest beam of light can be - so something that emits light for a VERY short time yielding in a short beam of light. (Normal speed and all (that's not the problem))
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  5. #4  
    Universal Mind John Galt's Avatar
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    Ah. You want to emit a single photon.
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  6. #5  
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    the amount doesn't matter as long as they occupy a minimal amount space - but with high intensity.

    i think my number 1 was confusing so just ignore it and go with 2 if possible....
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  7. #6  
    Universal Mind John Galt's Avatar
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    Then the shortest 'beam' is a single photon.
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  8. #7  
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    ok, that answers number 1, but how short a light-beam can our current technology produce in a controlled manner?
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  9. #8  
    Universal Mind John Galt's Avatar
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    I am pretty certain we can emit that single photon in a controlled manner. What is the context of your questions? It might make it easier to provide a more meaningful answer if we knew why you were asking.
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  10. #9  
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    i really cannot talk about the resaon for my question - but could you possibly explain to me how we can emit a single photon?

    i initially was unsure if we could, but i didn't assume we could achieve such an extremely low amount - i was hoping more in the range of 'a couple million' - i would need a high-intensity amount of light in a very short time (so that the overall beam of light can be in the nanometeres with many photons)
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  11. #10  
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    Quote Originally Posted by zyxstand
    i really cannot talk about the resaon for my question -
    Then, regretably, I cannot talk about the reason I wont answer.
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  12. #11  
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    You can use the electron to release a single photon, by creating higher potential gradient and then letting it return to its normal energetic state, the potential energy difference discharges a photon.
    "The present is theirs ; the future, for which I really work , is mine." Nikola Tesla
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  13. #12  
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    heh clarky - two problems:
    firstly, how can you completely isolate only electron!?
    and secondly, can you percicely time AND aim the direction of the emitted photon?
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  14. #13  
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    Quote Originally Posted by zyxstand
    heh clarky - two problems:
    firstly, how can you completely isolate only electron!?
    and secondly, can you percicely time AND aim the direction of the emitted photon?
    don't they run a large electrical current through a hydrogen atom and use an electromagnetic field to house the issolated electron?

    you can't, the photon is just the particle side of light consideration must also be given to the wave properties of light.
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  15. #14  
    Forum Freshman Yevaud's Avatar
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    Can you isolate an electron? Yes, though it's...wiggy to do. Electrons can be trapped just as positrons can. Isolating one is intensely difficult.

    What you are talking about is a single quanta, which always has a specific energy and a frequency:

    Q=hv

    Q = energy of a Quanta, in Joules (e.g., watts per/second)
    h = Planck's constant, 6.626 * 10^-34 Joules/Sec
    V = Frequency

    Solve for V, and your frequency of a Quanta is 3.6 * 10^8 Meters/Second.

    Call that a "pure" quanta. Unaffected by any outside influences.
    *Welcome, my friends, to the show that never ends*
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  16. #15  
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    hmm, i don't know how we got so off track - i actually don't need isolated individual light particles - but whatever.

    i think i just need to know whether it is possible to aim the direction of light at an instant (like a laser but without the charge-up time, etc.) and controll the amount as well.
    i guess to control the amount it would be possible to charge a immensley tiny plate (like a capacitor) and use that small stored energy to create light - however it would have to be done in a very short time...
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  17. #16  
    Forum Freshman Yevaud's Avatar
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    Ah. You're looking for the shortest pulse we can currently generate?
    *Welcome, my friends, to the show that never ends*
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  18. #17  
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    lmao Yevaud - that was so much more shorter than i could've put it.
    yes, that's exactly what i meant:

    what is the shortest light impulse we can generate.
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  19. #18  
    Forum Freshman Yevaud's Avatar
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    Now that is a damned good question. I'll look into it (if someone else doesn't beat me to it - not a lotta time this week, unfortunately), and try to get an answer back to you asap.
    *Welcome, my friends, to the show that never ends*
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  20. #19  
    Forum Freshman Yevaud's Avatar
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    Answer: 250 attoseconds: (1 Attosecond = 10^-18 of a second).

    The fastest stopwatch in the world


    The electromagnetic field of visible light changes direction approximately one thousand trillion times per second, so that the intensity of the light field varies from zero to maximum faster than a femtosecond (1 femtosecond being one thousandth of a trillionth of a second). By precisely controlling these hyperfast oscillations in a short laser pulse scientists from the Vienna University of Technology and Max Planck Institute for Quantum Optics in conjunction with their colleagues from the University of Bielefeld succeeded in developing the first measuring apparatus: An "ultrafast stopwatch". This apparatus is capable of measuring the duration of atomic processes with an accuracy of less than 100 attoseconds (1 attosecond being one tousandth of a femtosecond). A 250?attosecond X-ray pulse initiates the atomic process to be measured and the attosecond stopwatch at the same time. This new measuring method now allows for the first time observation of ultrafast processes in the electron shell of atoms.



    Full Abstract
    *Welcome, my friends, to the show that never ends*
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  21. #20  
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    WOW!
    firstly i find that really amazing because i'm from vienna :P
    well, since this is a stopwatch, are you telling me that it creates a continuous pulse of 250 attoseconds? quite fascinating - thnx!
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