Particles ?

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Fallingstar1971

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Are particles wave sources?

I ask because every model I see of the double slit experiment shows interference patterns from waves sourced from the slit. (light)

But under other conditions, the light acts like particle and only makes the expected 2 slits

None of the models show the light particles in motion emanating waves. The waves are always sourced at the slits and not as moving sources with the particles.

Am I misunderstanding something here?

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M

mabus

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As I understand it, they propogate as waves but can be induced to behave as particles. If you try to understand wave/particle duality I promise you're going to get a massive headache though. :lol:
 
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Jerromy

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The experiment is simple. Two slits in an obstruction, with a blotter behind the slits. When projectiles of a particular nature are fired at the slits there are 2 distinct "bars" in the blotter corresponding to where the projectiles would be able to avoid the obstruction by going through the slits. When the same experiment is done with light and the blotter is a type of film used in a camera for instance, the light transversing the obstruction through the slits makes a series of bars in the film rather than the pattern that simple straightline projectiles make. If you think about it logically then it makes sense that the slits would allow only waves of a certain phase through. When those waves travel through the slit they can be heading one direction in the wave or the other. The radiation at either side of the curve in a wave would be obstructed. The result is a pattern of bars I I I I rather than two bars I I.
 
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Fallingstar1971

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I think you misunderstand my misunderstanding.......my bad, let me put it another way.


If the particles are the sources of waves, and the particles move through the slits, on there way to the blotter, I would think that one would observe waves in all directions, and not just waves traveling from the slit to the blotter.


In other words, the particles, NOT the slits, produce the waves

If that statement is true, then waves should also be traveling backward twords the slits at the same time it is moving forward forming the slits

If THAT statement is true, than a pattern should also form on the slits themeselves.

Everytime I have seen this done, a small piece of cardboard was used to make the slits, so even if you looked there would not be enough surface for the pattern to form on. The cardboard used for the slits is pretty small.

I propose the following:

1. If light is a particle, then particles will pass through the slits

2. If light is a wave, then the waves should be focused by the slits, and the "light" speed should INCREASE on the other side of the slits. Like restricting a garden hose. ( yes I know you cant go faster than light, or I should say that "particles" cannot go faster than light. but what about waves?)

3. If light is a particle acting like a wave, then each particle emitts waves, so as each particle passed through the slit it would propagate light waves BACKWARDS!

4. I propose that the slit test be repeated, but using a box with equal sides, on side with the slits. This way we can observe the inside "side" that the slits are in to see if light waves propagate backwards.

5. Finnaly, I propose that the inside of the box be lined with an x-ray sensitive film

Light travels at many wavelengths. Is each wavelength a different kind of light? Or can one particle produce ALL kinds of light at the same time?

If one particle can produce ALL wavelengths, then the slits are only capturing a small amount of potential from the light. There are wavelengths passing through the box, others being reflected off the box

*sigh*

Its really hard to try and explain without visual aids. But picture this.

You have your light source, (laser, whatever)
This light is focused on the slits
This light is made of photons moving at light speed, focused or not.

Now you turn on your light source.

Traveling alongside your lightbeam is natural "unfocused" light. This is the light that reflects off the box and allows you to see. (yes its focused by your eyes, but compared to the light beam, unfocused. And it is traveling at the same speed as your focused light.)

But not ALL of that light is reflected, some is absorbed, some passed right on through (radio, gamma rays, x-rays,ect)
These rays should not loose there energy or speed. In other words, the box acts like a filter, only allowing "unfiltered" light in through the slits.

In x-ray light, there should be much more interference. Now the unfocused light should cause interference patterns with the focused light. And the slits SHOULD NOT matter at all in x-ray light. But something tells me that that is not the case. I get this feeling that x-rays are somehow going to follow the same rules as visible light, even though logic tells me that should NOT be the case.

I guess I should ask if the following statement is true. Light travels in ALL directions, but can only be observed if it is "inbound" to your current relative position.

If I could afford it, I would set this up myself. I can do it all except for the x-ray part. In fact, when I get out of work tonight I will do it all except for the x-ray part. I will post my findings either late tonight or tomorrow morning.

Any predictions?

Star
 
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Saiph

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I'll be honest, I haven't read most of your post this time, I'm budgeting my time today.

But no, particles are not wave sources. Particles are a class of behavior really, and not the source of anything. Waves are also independent, and not the source of particles.

Merging the two behaviors of light (and all matter actually) has been a major undertaking of quantum mechanics, and is a very...odd set of ideas to wrap your head around.

Light is either a particle, OR a wave, never both, and which it is depends on how you ask the question :) If you ask, "Are you a particle" by setting up an experiment to detect particle like behavior...you get a Yes. If you ask, "Are you a wave" by setting up an experiment to detect wave like behavior...you get a Yes.

The screwy thing is...it seems to know before you ask the question...

it's just...

weird.
 
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Fallingstar1971

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Using a laser pointer and foil, I was able to duplicate the double slit experiment.

However, as I was setting it up something occured to me.

If the particles were wave sources you would have less time to see it then it would take to see it.

In other words, the photons closest to the screen will propagate waves backward, but the photon behind it is propagating waves forward and they will cancel out.

Only the last photon in line would be able to create the pattern, and it would be gone before you could see it.

BTW the cool part wasnt in being right or wrong

The cool part was setting things up and seeing for myself. Seeing these patterns. I have seen the experiment before watching online lectures, but its not the same as doing it yourself.
 
K

kg

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Hi Fallingstar,
Have you checked out any of the lectures listed in the Space Science and Astronomy forum? If you go to the very first thread (Lectures Documentaries & Books (Science, Physics, Cosmology) and scroll down about two thirds of the way down the list (it's a long list!) you will find:
Lecture : Classical Physics 10 - Physics for Future Presidents (Unknown)
by Richard A. Muller from Berkley.
There are some lectures of his that deal with waves and light.
 
M

mabus

Guest
Saiph":ilmohodm said:
Light is either a particle, OR a wave, never both, and which it is depends on how you ask the question :) If you ask, "Are you a particle" by setting up an experiment to detect particle like behavior...you get a Yes. If you ask, "Are you a wave" by setting up an experiment to detect wave like behavior...you get a Yes.

The screwy thing is...it seems to know before you ask the question...

it's just...

weird.

Agreed totally on the weird comment.... but I do want to say that the idea that light is either a particle or wave is somewhat misunderstood.

Light is a wave, always. However light can be induced to BEHAVE like a particle. The wave seems to isolate in a small region and behave as if it was a particle, but it is still a wave.
 
M

mabus

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Fallingstar1971":11chyxpw said:
Using a laser pointer and foil, I was able to duplicate the double slit experiment.........
BTW the cool part wasnt in being right or wrong

The cool part was setting things up and seeing for myself. Seeing these patterns. I have seen the experiment before watching online lectures, but its not the same as doing it yourself.

I'm curious about the exact physical layout of your experiment. How did you set it up exactly?
 
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Fallingstar1971

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OK

Used a copy of "The Elegant Universe" to hold the laser pointer (it has a flat bottom)

I then raided my Sons Legos and constructed a mini-stand to pinch the foil and hold it in position

Then, on my coffee table, I wedged my drawing pad between one of my binders and a copy of "On the shoulders of Giants" by Hawkings. It was wedged in a way that was 90 degrees to the coffee table.

I cut three pieces of foil, and put slots in each one spaced at different amounts (I eyeballed one close to the diameter of the laser, the second slightly smaller so the outside edge of the laser would be touching both slits, and one 2 or 3 millimeters apart)

Putting the laser on one end of my coffee table, and the drawing pad on the other, I was able to slide the lego contraption back and forth while pointing the laser at the slits until the bars appeared.

I repeated the experiment with a flashlight held a few inches away from the foil and a more pronounced pattern appeared. ( I am colorblind and the regular flashlight produced more contrast and was easier for me to see)

I am sorry that I didnt take measurements, and I dont have a University Lab at my disposal, but its simple enough to repeat. My tape measure seems to have walked off ATM

Star
 
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Saiph

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light is also, always, a particle.

A wave cannot be induced to act as a particle, the characteristics of the two are mutually incompatible.

In the effort to reconcile them you cannot claim it is more particle than wave, or vice versa.

I assume you're using the image of a 'wave packet' that's arisen from quantum mechanics and their way of explaining probabilities of location in matter (e.g. electrons) and how solid matter can act like a wave?
 
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Fallingstar1971

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YES......I think


I was just trying to think how this could be possible

A particle that acts like a wave
A wave that acts like a particle
The particle and wave phenomena MUST be related

Then I started thinking about photons themselves as a wave source, and not a wave per say

But whenever I saw demonstrations of the double slit experiment, the wave sources were always the slits themselves, and not any particles moving through the slits.

So I thought about it for a while, and came to the conclusion that if the particles are wave sources, then an interference pattern should form on the same surface as the slits. In other words, turn the camera around.

So then I said to myself, "How could this be observed and duplicated. Thats when I got the idea for the experiment I outlined above.

Halfway through setting it up, it occured to me that even if the particles were wave sources, the "reverse" interference pattern would be canceled out by the next particle in line, as its waves are moving forward, the particle closest to the screen is sending waves backwards, and these two waves would cancel out.

As each photon hit the screen, either by reflection or absorbion it is effectively removed from the experiment. This "frees" the waves from the next photon in line and allows its waves to move forward and the pattern stays continuous.

However, when the very LAST photon of the experiment passes through the slits, it should produce a pattern AGAINST the slits. But this would happen so fast that it would be unobservable. There would be no continuous source of waves, just the one shot from the last photon in line.

Star
 
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Saiph

Guest
well, you've got a big problem with your arrangement....energy transfer.

If each particle is sending out a wave in all directions...

A) the energy has to come from somewhere...

b) You can't get a laser (massive side scatter is required in your arrangement!)

c) if only the 'wave' from the last photon survives...increasing the number of photons wouldn't increase the luminosity.

d) No image would occur on a photographic film until you turn off the light source (all previous 'waves' would be canceled by your interference scheme).


Sadly your idea doesn't match observations.
 
M

mabus

Guest
Fallingstar1971":2y74xqgc said:
OK

Used a copy of "The Elegant Universe" to hold the laser pointer (it has a flat bottom)

....

Then, on my coffee table, I wedged my drawing pad between one of my binders and a copy of "On the shoulders of Giants" by Hawkings. It was wedged in a way that was 90 degrees to the coffee table.

AWESOME choices :lol:

Thanks for the setup description. I think i'll do something like that for my neice and nephew, that sounds like a fun project for them.
 
M

mabus

Guest
Saiph":1v2uwrll said:
light is also, always, a particle.

A wave cannot be induced to act as a particle, the characteristics of the two are mutually incompatible.

In the effort to reconcile them you cannot claim it is more particle than wave, or vice versa.

I assume you're using the image of a 'wave packet' that's arisen from quantum mechanics and their way of explaining probabilities of location in matter (e.g. electrons) and how solid matter can act like a wave?

Exactly
 
S

Saiph

Guest
yes, but remember to use those exact same books, or else your results may vary :) (lol)

I liked that touch to the setup description btw, made me smile.
 
N

nailpounder

Guest
In 1801 Thomas Young concluded that light was a wave with the double split experiment. In 1905 Albert Einstein was
beginning to suspect that light was also a particle, and proved this with his "photoelectric effect" for which he won the nobel later. Thus the duality of light was born.

The photon is the quantized packet of energy (particle) that propagates through/with the field of the electromagnetic wave, it's energy is specific to the wavelength of which it propagates...................................Al
 
M

mabus

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nailpounder":pk7tk20o said:
In 1801 Thomas Young concluded that light was a wave with the double split experiment. In 1905 Albert Einstein was
beginning to suspect that light was also a particle, and proved this with his "photoelectric effect" for which he won the nobel later. Thus the duality of light was born.

The photon is the quantized packet of energy (particle) that propagates through/with the field of the electromagnetic wave, it's energy is specific to the wavelength of which it propagates...................................Al

There is no question that a "quantized packet of energy" is a particle. The question is, what is a particle? It is a contained area of energy (waves). We're not talking about marbles here as in the classic idea of atoms from the 1970's but rather a contained area of energy (waves).
 
J

Jerromy

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I can appreiciate your enthusiasm in experimenting to find out the truth... it never is as believable unless you see it for yourself, I know. One of the greatest disciplines in science however is eliminating unneccesary variables. Focusing your experiment of electromagnetic radiation in the visible wavelengths or x-ray wavelengths should not be construed as dependant on the other's inclusion. The difference between obstructions would be cardboard or lead plates but the result would be the same for either test subject. Perhaps a do-it-yourself at home variation could include visible light filters and varying slit configurations to see if different wavelengths of light produce different patterns. The likely outcome in my predictions is that the results will never mimic projectile trajectories and likewise projectile trajectories will never cause wave dispersion patterns. The reflective nature of the blotter being a minor influence of the results should not be a major concern for disputing a test that has been done millions of times in 200 years with the same logical conclusion... light acts like a "wave" whether it contains particles or not.
 
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