Chemical Forums
General Forums => Generic Discussion => Topic started by: rctrackstar2007 on May 19, 2006, 11:00:36 AM
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not sure if this is the right section for this q but anywho:
what does everyone think about light?
do you think it's a wave? a particle? or have you just accepted it as both?
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the commonly excepted theory seems to be that it has properties of both but personally, i have to lean more toward the side that light is a wave and not a particle
i'm sure people are going to argue with me on this but oh well
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i agree that's it's more of a wave. if it were a particle then space wouldn't be so vacuous (sp) now would it :o
but on the other hand light can be "felt" in a way and that would take momentum which requires mass which altogether requires it to be a particle.
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not sure if this is the right section for this q but anywho:
what does everyone think about light?
do you think it's a wave? a particle? or have you just accepted it as both?
It is now well known from experiments of interference, diffraction and photoelectric effects that light can act both as a light and wave. But it is difficult to feel. Let us know if you have something in mind - observation or experiment or question?
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who is us?
i already stated it's accepted as both so the constant repeat is unnecessary ::)
and when you stand in the sun, do you not "feel" it in a way?
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YOUNG's double split experiment IS the definitive explanation for wave particle duality I believe.
(sorry origionally said Thompson)
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http://hyperphysics.phy-astr.gsu.edu/hbase/mod1.html
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Here is brief explanation - http://en.wikipedia.org/wiki/Double-slit_experiment
Travels as wave - hits as particle.
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Here is brief explanation - http://en.wikipedia.org/wiki/Double-slit_experiment
Travels as wave - hits as particle.
would that not defy the laws of physics or something
does a car travel as a car and hit as a semi??
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how can it have particle properties and not have mass? or if it does have mass then how does it travel at the speed of light?
i would also agree with rc in that it defies the laws of physics to say that it travels as one thing and hits as another
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it bounces off of things like a particle doesn't it?
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the law that would defy would be the law of conservation of mass
a wave has no mass so it can't all of a sudden gain mass and hit as a particle
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Here is brief explanation - http://en.wikipedia.org/wiki/Double-slit_experiment
Travels as wave - hits as particle.
i can buy this. ^ it's all about energy.
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the law that would defy would be the law of conservation of mass
a wave has no mass so it can't all of a sudden gain mass and hit as a particle
E=MC2
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either way a particle won't accerate to the point where the negligable mass increases to that of one of a particle to hit hard enough
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Einstein helped to prove the wave particle duality with his observation of the photoelectric effect which says that if the photon is absorbed, some of the energy is used to liberate it from the atom, and the rest contributes to the electron's kinetic (moving) energy as a free particle.
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Travels as wave - hits as particle.
would that not defy the laws of physics or something
No - it actually defines them! :)
E=MC2
If you are seriously interested, read all about the Young's slit experiment - it is amazing. When there is only one slit the photons hit randomly on the other side wall as you would expect a particle traveling randomly to do. When there are two slits!!!! you get an interference pattern as if it were a wave travelling through the slits which gives an interference pattern as standard. THE CLEAVER PART is!!!!! if you only let one photon go at a time then it only EVER hits the opposite wall as part of the interference pattern - NEVER in the shaded parts of the interference patter - proving it travels as a wave as a single photon (if it were a particle - it couln't 'know' that there are two slits). :)
Not sure if what I wrote will make sense to you as a wrote it in a hurry (sorry - about to go home) so do read up on the Youngs slits expt. it IS the definitive explanation of wave particle duality!! (and its quite cool) 8) ;D :) - (That and the above mention of Einstein and the photoelectric effect to prove particle properties.)
Going home for weekend now - have fun.
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either way a particle won't accerate to the point where the negligable mass increases to that of one of a particle to hit hard enough
how hard are you talking about? we're not trying to destroy the earth with a beam of light here.
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Well anyways im going to post something so you guys will leave me alone and i can continue working on my math question which by the way is impossibe. so i have decided that since we looked through the slit and saw that light curved it is obviosly wavelike and since some experiments say that it behaves like a particle so their is obviously a logic conclusion being that it is both. well goodbye and have fun
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on the other hand sound could be used to prove the point that a wave can gain mass
sound is obviously a wave, but if you turn up the volume you can feel the bass or any other sound hitting you, if any of that makes sense
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on the other hand sound could be used to prove the point that a wave can gain mass
sound is obviously a wave, but if you turn up the volume you can feel the bass or any other sound hitting you, if any of that makes sense
you don't feel the sound, you feel the vibrations from the sub and/or whatever else is vibrating. I think i see what your saying though, sound waves can make your ear drums vibrate so you can hear the sound and things like that. Does that mean sound is a particle too though?
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pressure changes
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Borek nailed sound dead on.
I like the whole duality thing.
Now I'm not sure about this, but doesn't a Bose-Eintein Condensate slow down light?
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doesn't the theory of quantum mechanics say that everything is both a particle and a wave or am i just misinterpreting the definition
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Borek nailed sound dead on.
I like the whole duality thing.
Now I'm not sure about this, but doesn't a Bose-Eintein Condensate slow down light?
You are correct the Bose-Einstein Condensate can slow down light, in 1999 a group of scientists slowed it by 17 meters per second and then in 2001 they were able to temporarily stop a beam of light. i am not sure how to interpret this but does that mean that light has particle qualities or does this prove that it has wave qualities?
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pressure changes
Exactly. Sound is not a wave. If that were true, then sound could exist in a vacuum, but in a vacuum sound simply ceases to exist. Sound is a transfer of vibrational energy from one medium to another. You may ask then how come radio waves work? Well radio waves work because sound isn't transmitted via the waves. INFORMATION about the sound is transmitted. It's the receiver's responsibility to take that information and translate it back into recognizeable sound.
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wait if it is just a transfer than why do we have the speed of sound? and why does it refract/diffract (whichever) going from one medium to a different medium?
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Sound is not a wave.
Sound IS a wave.
Some waves are connected with the medium (like string, air, water surface), some are not (electromagnetic waves). Sound can exist as pressure waves in any medium capable of being pressurized, that's why it dissapears in vacuum.
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at a macroscopical level, things appear to be a wave (continuity). but at a microscopical level, things appear to a particle (discontinuity).
consider the Young split experiment. based on the result of the firing of just one photon, u will notice that it hits the detector at exactly ONLY one place. its only when a second photon comes, that amazingly, appears on the spot where a constructive interference pattern would be if a wave was transmitted rather. well not exactly, but the more photons you fire, the more likely it appears as a wave pattern with constructive and destructive interference.
therefore, to me, there is no problem distinguising the two, it is just from the context you look at, which is macroscopical or microscopical.
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if light is a particle, then shouldn't it stop soon after hitting water? because it's an actual object, tho small, hitting another one. such as when light hits a building or a human it stops, otherwise there would be no shadows.
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some radiation is particles and it will still travel some distance in water.
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but to what distance could a particle travel into a thick medium such as water?
surely a particle like that would come to a stop before the ocean actually becomes black at a depth
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from what i think, light will get "absorbed" into the water molecules, because light is like energy quanta, so the electrons in the water molecules will be excited to higher states.
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doesn't the theory of quantum mechanics say that everything is both a particle and a wave or am i just misinterpreting the definition
Well, it sounds good to me.
Wave particle duality suggests that the fundamental concepts of classical mechanics are false, in particular that waves and particles are not distinct entities - you simply have two ways of describing the same thing.
The problem is that everyone is brought up on classical physics, and so it is a difficult concept to get to grips with.
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Yeah, quantum theory is a very strange one. I read this very good book that talks about photons being at two places at one time and the fact that everything is a probability wave, until we turn around and observe it. Strange, but there is enough proof for it. When you first encounter it you are so frustrated by it because it makes no freakin' sense to you, you are only used to the classical physical world. I guess it becomes more understandable over time, once you get over the WTF moment ;)
So light is both a wave and a particle, but we can only observe wave and particle properties of light separately. That is, if we are looking to observe a wave prperty of light, that is what we will observe.
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I'm still in the WTF!? moment. I'll read more on it when I have a more advanced knowledge of math, mainly calculus. Some of the equations I've seen have gone clear over my head.
When I first stumble upon quantum mechanics, I was only 11, so it made no sense at all.
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I'm still in the WTF!? moment.
My "WTF? moment" lasted 2 years! For the first two years I treated quantum as a calculus exercise, with only a vuage idea about the physical consequences of the calculations. It's only in the last year or so that I have been able to understand (to a point) what it all means.
Someone wise once said that it is impossible to fully understand quantum mechanics, or something to that effect, but I can't remember who it was...
Actually I would compare understanding quantum with flying from one of the Hitchhikers guide books. You briefly fall through the world of quantum mechanics, but in order to stay suspended in it you have to you have to suddenly be distracted by something, and forget to come crashing down to hard ground of classical physics. No easy task.
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Someone wise once said that it is impossible to fully understand quantum mechanics, or something to that effect, but I can't remember who it was...
i have also seen that, but i cant exactly remember, though it was somewhat more of "no one can claim to understand all of quantum mechanics" :P
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Yeah, I still don't fully understand, I might never fully get it. I am in limbo between WTF and "I am just going to accept it". In my first semester of Pchem I went through the calculus and answered questions on the tests (more like spit it back to the professor ;)), but did not really try to get an understanding of what it meant physically. That happened much later, when I began to read on my own.
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yeah well your better off than i am :P. all i understand is the wikipedia version of quantum mechanics ::)
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I haven't taken the time to read all of the wiki stuff. I would have to question a lot of it though. If people in general have a hard enough time understanding it, then there must be a lot of myths out there about it or debunked theories that people follow which are prooven wrong. I have trouble trying to tell what has been scientifically prooven and what is still speculation.
Maybe someone will right a book entitled, "Quantum Mechanics for Dummies" that comes with a free "Calculus for Dummies" and also includes a synopsis of what has been scientifically prooven and what is only mere speculation, including the data, graphs, and equations.
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Polish professor of QC, W?odzimierz Ko?os, wrote a book "Elements of Quantum Chemistry explained in the non-mathematical way". I doubt it was translated to English, but AFAIR it was written in such a way that HS students should be able to understand.
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2 books i would highly reccomend (after reading them)
they are geared towards the general public IMO
is "Hydrogen : The Essential Element" by John S. Rigden
and "QED : The strange theory of light and matter" by Richard P. Feynman