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Thread: The acceleration of light?

  1. #1
    sub specie aeternitatis Pete Hanlin's Avatar
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    Anyone familiar with the current research going on concerning the "acceleration" of light? Apparently, a group of scientists have postulated that light travels through a certain gas at a speed faster than light travels through a vacuum. I've heard snippets about this research from a few sources now, but would appreciate a summary from someone with fuller knowledge.

    Pete
    PS- not that it has any ophthalmic applications, I'm just curious

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    Master OptiBoarder Jeff Trail's Avatar
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    Pete,
    Nice to know I'm not the only one who tracks things in optics other then the usual "what PAL do you like?" :) I have a whole bundle of web sights I usually track through and attached to this one is the A.P. about the story you are interested in. If you go to a search engine like MSN and type the words light barrier or something along those lines you'll find a slew of things on theoretical as well as published finds on alot of people tinkering in this field.. some really interesting things on theoretical and quantom physics as well...of course when this was published (the article below) they came out with others saying "nope" ..myself, I think we tend to try to think in a narrow given set of laws that are becoming outdated .. ask those same scientist (25 years ago) about some of the things we have now and they would say the say the same thing.."nope" never happen :)
    The last quote in the article from the scientist who said it wasn't correct strikes me as fairly funny :)
    I always considered science as an adventure not a set rule of guidelines ..thats the fun part taking a given and proving that it is wrong :)

    Jeff "here I thought I was just a "dumb" lab rat" Trail


    Light May Break Its Own Speed Limit

    By ALEX DOMINGUEZ
    .c The Associated Press

    Scientists have apparently broken the universe's speed limit.

    For generations, physicists believed there is nothing faster than light moving through a vacuum - a speed of 186,000 miles per second.

    But in an experiment in Princeton, N.J., physicists sent a pulse of laser light through cesium vapor so quickly that it left the chamber before it had even finished entering.

    The pulse traveled 310 times the distance it would have covered if the chamber had contained a vacuum.

    Researchers say it is the most convincing demonstration yet that the speed of light - supposedly an ironclad rule of nature - can be pushed beyond known boundaries, at least under certain laboratory circumstances.

    ''This effect cannot be used to send information back in time,'' said Lijun Wang, a researcher with the private NEC Institute. ''However, our experiment does show that the generally held misconception that 'nothing can travel faster than the speed of light' is wrong.''

    The results of the work by Wang, Alexander Kuzmich and Arthur Dogariu were published in Thursday's issue of the journal Nature.

    The achievement has no practical application right now, but experiments like this have generated considerable excitement in the small international community of theoretical and optical physicists.

    ''This is a breakthrough in the sense that people have thought that was impossible,'' said Raymond Chiao, a physicist at the University of California at Berkeley who was not involved in the work. Chiao has performed similar experiments using electric fields.

    In the latest experiment, researchers at NEC developed a device that fired a laser pulse into a glass chamber filled with a vapor of cesium atoms. The researchers say the device is sort of a light amplifier that can push the pulse ahead.

    Previously, experiments have been done in which light also appeared to achieve such so-called superluminal speeds, but the light was distorted, raising doubts as to whether scientists had really accomplished such a feat.

    The laser pulse in the NEC experiment exits the chamber with almost exactly the same shape, but with less intensity, Wang said.

    The pulse may look like a straight beam but actually behaves like waves of light particles. The light can leave the chamber before it has finished entering because the cesium atoms change the properties of the light, allowing it to exit more quickly than in a vacuum.

    The leading edge of the light pulse has all the information needed to produce the pulse on the other end of the chamber, so the entire pulse does not need to reach the chamber for it to exit the other side.

    The experiment produces an almost identical light pulse that exits the chamber and travels about 60 feet before the main part of the laser pulse finishes entering the chamber, Wang said.

    Wang said the effect is possible only because light has no mass; the same thing cannot be done with physical objects.

    The Princeton experiment and others like it test the limits of the theory of relativity that Albert Einstein developed nearly a century ago.

    According to the special theory of relativity, the speed of particles of light in a vacuum, such as outer space, is the only absolute measurement in the universe. The speed of everything else - rockets or inchworms - is relative to the observer, Einstein and others explained.

    In everyday circumstances, an object cannot travel faster than light.

    The Princeton experiment and others change these circumstances by using devices such as the cesium chamber rather than a vacuum.

    Ultimately, the work may contribute to the development of faster computers that carry information in light particles.

    Not everyone agrees on the implications of the NEC experiment.

    Aephraim Steinberg, a physicist at the University of Toronto, said the light particles coming out of the cesium chamber may not have been the same ones that entered, so he questions whether the speed of light was broken.

    Still, the work is important, he said: ''The interesting thing is how did they manage to produce light that looks exactly like something that didn't get there yet?''

    AP-NY-07-19-00 2003EDT

    Copyright 2000 The Associated Press. The information contained in the AP news report may not be published, broadcast, rewritten or otherwise distributed without the prior written authority of The Associated Press. All active hyperlinks have been inserted by AOL.

  3. #3
    Master OptiBoarder Darryl Meister's Avatar
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    I wouldn't throw away your physics books just yet... This sounds a lot like those guys who claimed that they had managed to perform "cold nuclear fusion."

    Best regards,
    Darryl

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    That Boy Ain't Right Blake's Avatar
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    Aephraim Steinberg, a physicist at the University of Toronto, said the light particles coming out of the cesium chamber may not have been the same ones that entered, so he questions whether the speed of light was broken.

    Light has both wave-like and particle-like properties. This experiment relies on the "leading edge", a wavelike property, which allows the light exiting the cesium chamber to "predict" the waveform of the light based on what enters the chamber. What doesn't seem to be happening is a particle of light traveling faster than the speed of light, which would truly be an achievement.
    If this experiment doesn't go the way of cold fusion and the perpetual motion machine, maybe they'll find some use for it, but it won't be "warp speed" space travel...

    Blake

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    Master OptiBoarder Jeff Trail's Avatar
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    Blake,

    Finish his quote though .. not just the "negative" part of it .. get it positive negative quirks.. oh forget, Physics is not "humor" conductive (cheap pun as well :)
    He went on to say the trick is how exactly did you get something coming out before it even finished getting there :)
    I figure since you can't creat something from nothing (light in this case) then something happend. As for the "cold" fusion thing. That was a little harder to prove as well as duplicate, as we all seen.
    But the benifits to this would be far greater, just think what it would do communication.. since it would basically along the same principal as optic fiber which we know moved from electrical impulse to light impulse to carry voice and data..
    I still think it was an interesting article and if it does pan out maybe Corning won't snag up this technology like they did with the fiber :) ..
    BTW any of you guys follow a company called TUT System ? They came up with a way for you to use one copper line (well it's dual lines as all copper based lines are) BUT they came up with a way to "stack" impulses on the same leads.. you can talk, transmit and be on line all at the SAME time and it being one line.. it's the program Time Warner is basing its "road runner" concept on.

    Jeff "grind'em if ya got'em" Trail

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    That Boy Ain't Right Blake's Avatar
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    After reading this article http://www.washingtonpost.com/wp-dyn...2000Jul19.html
    I'm less skeptical about this "speed of light" experiment. Apparently, they were able to reverse the way light is bent when it passes through a medium by zapping the cesium vapor with lasers. The resulting was a medium with a refractive index less than 1.
    It remains to be seen whether there will be any practical uses for this data. Something akin to fiber optics would be the most likely application, I would think... but can you imagine miles and miles of cesium vapor chambers with a bunch of lasers firing at them? Probably not very cost effective.

    BTW Pete - "acceleration" is the rate of change of velocity (speed) with respect to time... :-)

    Blake

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    sub specie aeternitatis Pete Hanlin's Avatar
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    Not to quibble over vocabulary, but "acceleration" is defined by Webster as "to quicken- to speed up." Isn't that what introducing light to the cesium vapor is effectively doing (i.e., "speeding up" light)?

    All this to ask, "What term should I use to describe the cesium vapor's effect on light so as not to look like the scientific lightweight I am when discussing this issue with more knowledgeable company?" ;)

    Thanks for the reference to the article, BTW... interesting stuff

    Pete "suddenly not feeling very voluble" Hanlin

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    Master OptiBoarder Jeff Trail's Avatar
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    Originally posted by Pete Hanlin:
    Isn't that what introducing light to the cesium vapor is effectively doing (i.e., "speeding up" light)?

    All this to ask, "What term should I use to describe the cesium vapor's effect on light so as not to look like the scientific lightweight I am when discussing this issue with more knowledgeable company?" ;)
    Pete,
    I guess it would depend on how you look at it, did they actually speed up light or reduce resistance and the result was that light traveled a set distance "quicker" then in normal resistance.
    When you figure that before the light wave was there it was traveling at a "normal" speed but when it left the "box" it was back to a maintained regular "acceptable" speed then it was only traveling beyond the accepted normal speed inside the box.. so the result, I would think is that it's the medium not the actual light that was having the effect induced on the accelaration , or in this case the distance it traveled from point A to point B.
    I would think if you accelarated something in the literal since of the definition then you would have to stay with the laws of physics.
    Here is the part I find interesting, you have a beam of light being measured moving from point A to point B . to increase movement , you have to do one of two things, increase the actual physical energy there by accelrating the speed or you reduce the resistance that effect the speed.. right?
    What I found most interesting was the light going in was traveling at a set speed and it left the box at the SAME speed but it actually traveled quicker between those two points inside the box.. I look at it like this.. say I'm rolling a ball across a floor from point A to point B.. now right in the middle I place a patch of oil.. when the ball hits the oil it's resistance is less and without the friction it passes over the "oil spot" quicker.. BUT when it leaves the "oil spot" it still is traveling faster by the speed that was gained by reducing friction.. the thing I found interesting was that the light was traveling no faster in measured speed entering the box then leaving it..actual physical speed, the shortened distance, translated to greater acceleration, was only inside the box.. hmmm..

    Oh well it's fun to tinker with but what does a dumb lab guy know about physics

    Jeff "hated physics and trig in school..go figure" Trail


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    That Boy Ain't Right Blake's Avatar
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    Pete, I see now where you were coming from when you used the word "acceleration". That's exactly what is happening! When you press the accelerator in your car, it speeds up. Thus, any time you have a change in velocity, or speed, acceleration is taking place.
    Jeff (your turn now), by definition, index of refraction is the speed of light in a vacuum divided by the speed of light in a given medium. So when light enters a medium, its speed changes - it accelerates. Normally, though, the acceleration is negative (it slows down). One of the laws of physics (I'm paraphrasing) is that something that is at rest will stay that way unless something causes it to move. The same holds true for speed - an object will speed up or slow down if acted on by some force, such as friction. What the physicists did was bend the light waves in such a way as to decrease the resistance.

    "Darnit Jim, I'm an engineer, not a physicist!"

    Blake

    [This message has been edited by Blake (edited 07-27-2000).]

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    Master OptiBoarder Jeff Trail's Avatar
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    Originally posted by Blake:
    Jeff (your turn now), by definition, index of refraction is the speed of light in a vacuum divided by the speed of light in a given medium. So when light enters a medium, its speed changes - it accelerates. Normally, though, the acceleration is negative (it slows down). One of the laws of physics (I'm paraphrasing) is that something that is at rest will stay that way unless something causes it to move. The same holds true for speed - an object will speed up or slow down if acted on by some force, such as friction. What the physicists did was bend the light waves in such a way as to decrease the resistance.
    Blake,

    I'm sure almost everyone finds this fairly boring and I don't want to move off into something as confusing as Planck's constant or wave mechanics.. BUT (don't you just love that word :)) wouldn't this almost be the opposite of Planck's constant? where you don't have something occupying the same "space" but actually it was the same thing in different "space" at the same time! :) It was leaving (I take it at the same accelerated speed it was entering but it was passed the point where it should have been if it was reacting to the accepted speed of light
    Say if you applied the principles of wave mechanic's (Quantum physics) it was actually accelerated between to points mid way between point A and point B.. right? but what I can't figure out is if you accelerate the speed it was traveling then why would it end up the same speed as it entered as it was leaving? theoretically (or I would think) since it is a "wave" of light that does not have the same things effecting it as, say my ball example.. where friction would reduce the speed then why wouldn't the acceleration once it entered be constant after it left the vapor chamber? ..I didn't see where any of that was mentioned..Oh well I guess most everyone is bored to tears now :) but I find it interesting to think about.. even if it doesn't have a cylinder and axis !! :) I would think based on particle acceleration theory, once you have accelerated the speed of the medium (this case light) that it would continue at the higher acceleration until it was effected by the unknown constant (gravity etc. etc.).. Oh well, maybe I should stick to grinding .50 spheres and keep my lab rat whiskers out of Quantum physics.. :)

    Jeff "always just a lab rat" Trail


  11. #11
    That Boy Ain't Right Blake's Avatar
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    Well, it sure has been nice to put my Accufitter down long enough to discuss something interesting (to me anyways). Unfortunately, I've only had one semester of quantum physics, so it's not easy to make sense of the work of a bunch of PhD's. Nevertheless, I'm going to try :-)
    I think the key to the cesium thing is that they bent to light waves, stretching them out. We know that the speed of light is the product of its frequency and its wavelength. So, if you were able to increase the wavelength (by stretching the wave) while maintaining the same frequency, the speed would increase. Have you ever noticed on Star Trek when they go to warp speed the ship seems to stretch out into space?
    I also find it interesting that the increased speed it not maintained once the light exits the chamber. I couldn't find any info on this, so I can only guess that the time it takes to decelerate is very minute. Another possibility might be that it speeds up then slows down inside the chamber. But these are just guesses.
    Well, I wanted to get my 2 cents in on this subject, but it's starting to feel more like a dollar...

    Blake

    [This message has been edited by Blake (edited 07-28-2000).]

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    Forever Liz's Dad Steve Machol's Avatar
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    Confused

    Geez you guys! There are sure a lot of long-winded explanations for something that may not have even happened! ;)

    I'm with Darryl on this one. Until it can be duplicated by other researchers, then I'd be cautious about taking this at face value just yet.

    And I'm sorry to be the one to break this to you Blake, but that Star Trek stuff is actually science fiction (with particular emphasis on fiction.) :D

    [Note: Don't take my comments too seriously. I think this has been a very interesting and thoughtful discussion.]

    ------------------
    Steve
    OptiBoard Administrator

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    sub specie aeternitatis Pete Hanlin's Avatar
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    Redhot Jumper

    Ohh, ohh! Call on ME! I know this one!

    The reason the light slows down after leaving the cesium is the same as why light speeds up when it leaves a lens- a change in index.

    Imagine a bar of water suspended in mid air (just a freestanding rectangularly shaped body of water without a container). Now, drop a ruler above it. The ruler speeds through the air- but slows when it enters the water. It proceeds through the water at a slower speed- until it exits the water and resumes its "in air" speed.

    The opposite is happening in this example. The light slows coming out of the cesium because it is encountering greater resistance. The interesting thing to me is that this implies that light must have momentum (which I have always understood only applies to objects with mass, which light does not have). In the water column example, the driving force on the ruler is gravity- what is the driving force for the light, and how can it have momentum if it has no mass? I suppose if light has a certain level of energy inherent to it... but if light is simply energy, shouldn't the energy of light be tending toward a more disorganized state (keeping with the Laws of Thermodynamics)?

    Pete "Wish I had paid more attention in H.S. physics..." Hanlin

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    Master OptiBoarder Jeff Trail's Avatar
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    Originally posted by Blake:

    I think the key to the cesium thing is that they bent to light waves, stretching them out. We know that the speed of light is the product of its frequency and its wavelength. So, if you were able to increase the wavelength (by stretching the wave) while maintaining the same frequency, the speed would increase.... speed it not maintained once the light exits the chamber. I couldn't find any info on this, so I can only guess that the time it takes to decelerate is very minute. Another possibility might be that it speeds up then slows down inside the chamber.
    Blake
    Taking some of this and some of what Pete is talking about in his posting about "mass & energey" ..snipping the "star Trek" stuff :) and giving the ole to Steve :)
    Here is where I can add the two together and have another question, knowing of Planck's constant.. here is what I can't understand, taking Pete's statements one step further, under Planck's constant you know that it's not supposed to be feasible to have the two seperate things occupy the same physical location at the same time.. so moving right along if you increased the speed of light, which would mean an increase of out put of energy..which means the molecular structure would have increased activity, since it's energey and not an actual physical mass.. then it would appear to me that it would like having a chain reaction..where as one thing bumps into another into another so forth and so on.. so if it was increased inside of the chamber then it would actually "push" the light coming out to an increased rate of acceleration right?.. unless you want to throw Planck's constant out the window as well :)

    Oh well something to think about I guess :)

    Jeff

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    Forever Liz's Dad Steve Machol's Avatar
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    Posted by Jeff:
    .. unless you want to throw Planck's constant out the window as well.
    Not only should we throw out Planck, but let's get rid of out all those useless Republicans and Democrats as well! It's time we had a Congress that had the guts to repeal the laws of physics!

    Steve
    "186,000 miles per second. It's not just a good idea - it's the law!"

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    Master OptiBoarder Darryl Meister's Avatar
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    Hey, just a couple of pointers for all you physics buffs out there...

    1) Acceleration is not just a change in speed, it can also be a change in direction. Specifically, acceleration is a change in velocity, which is a vector quantity with both a speed and a direction. For instance, if you go around a curve at 60 mph you are technically accelerating, since you are changing direction.

    2) The stretching out of spaceships in movies has to do with the theory of relativity, including "length contraction" and "time dilation." I don't remember whether the spaceship is supposed to lengthen or shorten for the movie-watcher's perspective, though -- so they may still have gotten it wrong.

    Best regards,
    Darryl "relativity can be demonstrated by getting stuck on a 7 1/2-hour flight from Southbridge to San Francisco!" Meister

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    That Boy Ain't Right Blake's Avatar
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    The reason the light slows down after leaving the cesium is the same as why light speeds up when it leaves a lens- a change in index.
    BINGO!

    ...if light is simply energy, shouldn't the energy of light be tending toward a more disorganized state (keeping with the Laws of Thermodynamics)?
    The energy of light does exactly that. The "driving force" behind the photons of light is the source from which they emit, such as a light bulb. If you stand 1 foot from a light source, it will be brighter than if you were standing 10 feet from it. This is because light tends to dim as it gets further from its source. You might notice that the light coming out of the cesium chamber was dimmer than the light that entered.

    As for the news about Star Trek not being real, the Easter Bunny was kind enough to explain that to me a while back :-)

    Blake

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    Master OptiBoarder Darryl Meister's Avatar
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    Originally posted by Darryl Meister:
    2) The stretching out of spaceships in movies has to do with the theory of relativity, including "length contraction" and "time dilation." I don't remember whether the spaceship is supposed to lengthen or shorten for the movie-watcher's perspective, though -- so they may still have gotten it wrong.
    Actually, now that I've been thinking about this a bit more... Are the spaceships really stretched out in the movies, or are they just leaving a trail of light behind them -- perhaps to simulate that the ship is traveling as fast (if not faster)? Hmmm...

    Best regards,
    Darryl

  19. #19
    Master OptiBoarder Darryl Meister's Avatar
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    Originally posted by Blake:
    ...if light is simply energy, shouldn't the energy of light be tending toward a more disorganized state (keeping with the Laws of Thermodynamics)?
    ... If you stand 1 foot from a light source, it will be brighter than if you were standing 10 feet from it. This is because light tends to dim as it gets further from its source.
    Hi Blake,

    Radiation becomes less intense at farther distances because the same amount of energy falls on larger and larger areas. Specifically, since the energy from a radiation source is spreading out in all directions, the intensity of that energy is inversely proportional to the square of the distance from the source (1/D^2). At 1 ft from the source, a given amount of energy occupies 1 square foot of area. At 10 ft from the source, the same amount of energy now occupies 100 square feet. "Energy becoming more disorganized" is related to thermodynamics, but I believe that is has more to do with "entropy" and energy that changes its state (from work to heat for instance).

    Best regards,
    Darryl

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    sub specie aeternitatis Pete Hanlin's Avatar
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    Since a laser doesn't "spread out" (as much, anyway), does it retain its intensity over distance? Also, does light have "momentum?"

    Pete

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    Bad address email on file Darris Chambless's Avatar
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    Redhot Jumper

    Hey everyone,

    "(which I have always understood only applies to objects with mass, which light does not have)."

    Just thought I'd drop in and clarify a few things for ya'll :-) First, it hasn't been discovered yet but light does have mass. It is simply immeasurable with todays equipment and standards for its properties. Secondly, since it does have mass it can have momentum as well. Cesium isn't the only gas that can cause this reaction and isn't really speeding light up, but that will be found out later on in life ;-)

    I would like to know more about the properties of cesium.

    I would speculate that the light that exits the chamber is not the "entering" light at all but the energy produced by the reaction between light and the properties of the chamber. An assimilation so to speak or a "copy" but not the original. That in itself could throw a wrench in the "faster than the speed of light" thing. The reason the light appears to exit before it enters the chamber is because it begins its reaction before it clears the barrier or sanctum as it were ;-)

    Now with all that said I could be wrong, but my guess is as good as anyone else :-)

    Have fun and I would have to say that eventually the "physics book" will have to be thrown away. If I could only tell you why :-)

    Darris "I've been through the Time Tunnel and back once or twice :-)" Chambless


  22. #22
    Master OptiBoarder Darryl Meister's Avatar
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    Originally posted by Pete Hanlin:
    Since a laser doesn't "spread out" (as much, anyway), does it retain its intensity over distance? Also, does light have "momentum?"
    You're right about the laser; that's one of its principal advantages. Lasers produce intense light sources (with less power) because they are highly collimated and coherent beams of light. This is also why they can travel thousands of meters. I believe that the intensity of a laser beam would still drop, however, because of things like atmospheric scatter, absorption, and such -- albeit it rather gradually.

    "Particles" of light have no mass, but they still have momentum. Momentum for normal objects is defined as mass times velocity. Momentum for photons is defined as Planck's constant divided by wavelength. Actually, the equation for the momentum of a photon also applies to normal objects, as well. Objects, including tennis balls, have a de Brgolie "wavelength" -- even though wavelengths for these objects are very, very small.

    (Don't be too impressed -- I have my college Physics book handy...)

    Best regards,
    Darryl

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    Master OptiBoarder Jeff Trail's Avatar
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    Darryl,

    What are you talking about? I threw Planck's constant out there and Steve tossed it right out the "window" :) ..
    Now that Darris has jumped into the debate :) it wasn't "leaving before it got there" ..that wouldn't have been wave mechanics but more like the "twilight zone" :)
    Atleast nice to know I'm not the only one who actually had to read up on Planck and the worst part is after being out of school for better then 10 years it actually stuck with me.. the Prof. would have been proud of me :)

    Jeff "very funny Scotty..now beam down my clothes" Trail ....or if you prefer since we are talking physics

    ""If electricity is produced by electrons, is' morality produced by morons??"

    [This message has been edited by Jeff Trail (edited 08-01-2000).]

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    Master OptiBoarder Darryl Meister's Avatar
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    In all fairness, Planck's constant is close to the end of most books! ;) The universal gravitational constant is usually one of the first ones you run across...

    Best regards,
    Darryl

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    Objection! OptiBoard Gold Supporter shanbaum's Avatar
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    2,974

    Confused

    I refer those of you interested in reading something intelligible about this topic to page 26 of the September 2000 issue of Scientific American.

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