Can I ask a question here rather than main, I end up here anyway.

The patterns captured on the screen appear as stripes, as you say. The photon is described as a wave-particle, and the only thing recorded on the screen is where the particle hits. The stripes are caused by wave interference on the premise that the wave nature of the photon (or any particle) can go through both slits and interfere with itself, causing the familiar wave interference images. That interference takes place in the space between the slits and the screen, and the affect of the interference going on in that space influences where the photon, in its particle state, will be detected by the screen. The particle can only go through one slit, so the position where the particle strikes the screen is said to be influenced by the wave interference cause by the wave going through both slits. It is interesting to note that even if only one photon is sent toward the slits at a time, you still get the stripes when both slits are open. This is considered evidence that the single photon is both a wave and a particle, and its wave interference pattern is somehow able to cause the particle to strike the screen primarily in the stripe pattern, even when only one photon is sent at a time.

 

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Thank you for your post, does the light that leaves the slit not follow the inverse square law? even as a single particle?

 

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I'm not sure about applying the inverse square law; I'd have to look it up. Give me an example. When light passes through a pinhole smaller than its wavelength, it emerges as a spherical wave on the other side. The slits act much like pinholes, and the two slits result in two separate spherical waves from one photon in its wave state, since the waves are purported to go through both slits, and interfere with themselves. The particle only goes through one slit, from what I understand, and only the particle is recorded on the screen, but I'm repeating myself, lol. Perhaps someone else can be more helpful.

 

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Forget the inverse square law and stop asking more questions, especially on quantum theory, until you have read and taken in what an interference pattern is and how it arises. Until you get your head around this concept there is no point whatsoever in going any further on this topic. You will just add to the muddle in your head. Go step by step. Please!

You get interference patterns with water waves too, but of course they are not light and dark bands, they are wavecrests and troughs and areas of slack water. Read this for example: http://en.wikipedia.org/wiki/Interference_(wave_propagation)

 

I am going by step by step starting with the stripes, I want to try and visualise the effect in my mind, the dark stripes are the absence of light, the light stripes are light, I see a fan effect , I do not see how this is a wave.

I am working from the screen backwards to the slit and then to the source, wait until I get to the slit and start asking about if the slit has any gravitational field in the slit itself.

 

Have you read any of the things I suggested you read? Until you do that, you will not progress. Read about interference between waves and then we can talk about the light and dark bands in an interference pattern of light waves.

 

I have read the links and do not understand it, so that is why I started with the patter on the screen, I can not visualise the wave hitting the screen and becoming stripes, I see no mechanism and observe the inverse square law every time I try to picture it.

 

Forget the sodding inverse square law. It has bugger all to do with anything here. Look, when two waves overlap, if the crests and troughs are aligned, because they are " in phase", then they reinforce, making bigger crests and troughs, right? That's constructive interference. If the crests of one wave align with the troughs of the other, because they are "out of phase", they cancel each other out. That's called destructive interference. Right?

You can get this with water or light. With water, you get bigger humps and dips where the waves are in phase and flat water when they are out of phase. From experience rowing on the Thames in London, I know that when you get a wash of a cruiser reflecting off the walls at high tide, there are points at which the incoming waves from the cruiser reinforce the ones reflected off the wall. That is hell for a racing shell: Sometimes you can't keep your oars clear of the waves and the balance of the boat is always upset badly.

The height of the crest of a wave (or the depth of a trough, since waves are symmetrical), compared to the level of flat water, is called its amplitude.

Now with light, the amplitude of the wave (the maximum strength of its oscillating electric and magnetic fields, since it is an electromagnetic wave) correlates with how bright the light is. So, two reinforcing waves create a brighter spot and two cancelling waves create a dark spot. So what you see in the slit experiment is light bands where the waves reinforce each other and dark bands where they cancel. Please note you will only see this effect with coherent monochromatic light, i.e. light which is all of the same wavelength and all in phase.

There are some pictures of what you get with single and double slits here:http://www.colorado.edu/physics/phys1140/phys1140_fa04/Expts/O4Fall04.html

 

So it hits the wall like this ?

Sorry I have to be able to visualise a process to understand it.

 

Anything to do with it ?

1. Interlacing is the practice of displaying a single frame of video as two 'half' frames. Each frame is split into alternating lines, so that the first frame displays lines 1,3,5 and so on, while the second frame of the pair displays lines 2,4,6 and so on.

 

No Irrelevant. You are posting too fast. Slow down, read and think.

And stop adding new extraneous ideas all the time. If you do that you will add to the confusion. One step at a time. Look at the material I have given you and think about it.

 

Does the interference wave make surface contact with the background screen, like my diagram? Is this why the stripes are perceived?

I have looked at you links , and can at the moment visualise the interferences waves like in my diagram, I also noticed the slits in the link are angled, is this always the case?

I am trying hard to visualise the process, thank you for the patience.

 

Your picture is two dimensional and the waves are more than wave fronts. Look at the graph on the left side in this link, http://en.m.wikipedia.org/wiki/Interference_(wave_propagation)#Mechanism, it shows how wave meet constructively and destructively.

 

Yes, if you want to see where the constructive and destructive interference are occurring, you put a screen in the path of the beam and let it light it up. And in fact, if you move the screen towards or away from the the light source, the interference pattern will change, because you will be intercepting the light at a different point, so some of what were crests may now be troughs and vice versa.

Re the "angled slits", there is problem with light in that the wavelength is very short - of the order of half a micron or so. If you have square-cut edges to the slits in the plate, you will get waves starting from both front and rear corners, maybe reflecting off the opposite side of the slit and generally muddling everything up. So you cut them at an angle, in order to give a really knifelike, sharp edge to the slits, less that half a micron in thickness and with no possibility of unwanted reflections. It's just to make the experiment a clean one.

Don't get hung up on that though. The important point is the phase of the waves and whether they interfere constructively or destructively at a given point in space.

 

Ok thank you . I can now visualise the process and understand what is happening .