Double-Line Exp: Seeing Interference Pattern Explained

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In summary, the conversation revolves around the observation of an interference pattern when drawing two vertical lines close to each other and viewing them from a short distance. The participants discuss the potential explanations for this phenomenon, including the role of optical illusions and the difference between this pattern and the double-slit experiment. The conversation also touches on the importance of using good monochromatic light for interference patterns and the limitations of relying solely on visual detection.
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forcefield
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If I draw two vertical lines close to each other and watch them from a short distance then I can see an interference pattern. How do you explain it ?
 
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forcefield said:
If I draw two vertical lines close to each other and watch them from a short distance then I can see an interference pattern. How do you explain it ?

This is vague.

Using your eyes as your primary detector is seldom a good idea. I am sure you know all about optical illusions, etc. How would you know that what you are seeing isn't an optical illusion? If it is, this is now a biology/medical science topic, not a physics topic.

Zz.
 
  • #3
If I draw two vertical lines close to each other and watch them from a short distance then I can see an interference pattern.

I had to try it to see what you meant. I don't believe this is an interference pattern. I believe it has more to do with the eye's inability to focus on close objects. When too close the lines appear out of focus (eg spread out) on the retina. This allows the image of one line to partially overlap with the image of the other line producing a third line in the middle. This effect is similar to..

http://michaelbach.de/ot/sze_Frankfurter/index.html
 
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  • #4
forcefield said:
If I draw two vertical lines close to each other and watch them from a short distance then I can see an interference pattern. How do you explain it ?

ZapperZ said:
Using your eyes as your primary detector is seldom a good idea. I am sure you know all about optical illusions, etc. How would you know that what you are seeing isn't an optical illusion? If it is, this is now a biology/medical science topic, not a physics topic.

Hmm, I don't know ALL about optical illusions. I think that seeing the interference pattern in this case must be an optical illusion because I just draw the lines myself.

Are you saying that this phenomenon is different from the double-slit experiment (i.e. light from two slits/lines interfering and causing the pattern ?
 
  • #5
forcefield said:
Are you saying that this phenomenon is different from the double-slit experiment (i.e. light from two slits/lines interfering and causing the pattern ?

Absolutely.
 
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  • #6
forcefield said:
If I draw two vertical lines close to each other and watch them from a short distance then I can see an interference pattern. How do you explain it ?
There are two critical differences here. A simple interference requires monochromatic light (as with a laser). Also, the interference pattern is projected onto a screen without any optical focusing. When view by the eye, it would be difficult to defocus your eye enough to get the interference pattern to fall on the retina.

If we set aside the double slits for a moment and simply look at a rough surface illuminated with laser light, you will see an interesting pattern of constructive and destructive interference. It's called "laser speckle".
 
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  • #7
forcefield said:
Hmm, I don't know ALL about optical illusions. I think that seeing the interference pattern in this case must be an optical illusion because I just draw the lines myself.

Are you saying that this phenomenon is different from the double-slit experiment (i.e. light from two slits/lines interfering and causing the pattern ?

Use your camera and put it at the same distance. Snap a photo. Does it see the same thing that you see?

End of story.

Zz.
 
  • #8
There is exactly the same diffraction pattern from two lines as two slits (of the same dimensions). Both are due to obstructions in the arriving wavefront. The two patterns add up to a uniform illumination of the 'screen'. So it's not a totally crazy idea at all. The difference is in the visibility. The two slit pattern is usually viewed in subdued (or zero) ambient light and you easily see the tiny amount of energy that gets through the slits. When you are looking at the pattern from two lines, what you can see is all the incident wave, less the tiny amount that is obstructed by the lines. Visibility is many orders of magnitude less. With the right optics, it is quite possible to see the side fringes from two lines but I doubt that you were actually observing that.

.Scott's comment about needing good monochromatic light is even more relevant in the case of the lines.
 
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  • #9
ZapperZ said:
This is vague.

Using your eyes as your primary detector is seldom a good idea. I am sure you know all about optical illusions, etc. How would you know that what you are seeing isn't an optical illusion? If it is, this is now a biology/medical science topic, not a physics topic.

Zz.
Well it's the only primary detector we have got I doubt very much that the camera or any other usefull device could be built using sound smell or hearing.Maybe you could think one into existence.
Optical illusions are detected by the eye and all instruments in there manufacture are crafted from the input of vision.If you really look at the subject closely I doubt you could without the aid of sight at some stage in your life.
 

FAQ: Double-Line Exp: Seeing Interference Pattern Explained

1. What is the double-line experiment and how does it work?

The double-line experiment, also known as the double-slit experiment, is a classic experiment in quantum mechanics that demonstrates the wave-particle duality of light and matter. It involves sending a beam of particles, such as photons, through two closely spaced parallel slits onto a screen. The resulting interference pattern on the screen shows that the particles behave like waves and interfere with each other, creating a pattern of light and dark bands.

2. What is the significance of the interference pattern in the double-line experiment?

The interference pattern observed in the double-line experiment is significant because it shows that particles can behave like waves and exhibit interference patterns, which was previously thought to only be possible for waves. This challenges our classical understanding of particles and suggests that they have wave-like properties.

3. How does the double-line experiment support the wave-particle duality theory?

The double-line experiment provides evidence for the wave-particle duality theory by demonstrating that particles can behave like waves and exhibit interference patterns. This supports the idea that particles have both wave-like and particle-like properties and that their behavior is dependent on the method of observation.

4. Can the double-line experiment be performed with other particles besides photons?

Yes, the double-line experiment has been performed with other particles besides photons, including electrons, protons, and even molecules. The resulting interference patterns have been consistent with the wave-particle duality theory and have further supported its validity.

5. How has the understanding of the double-line experiment evolved over time?

The double-line experiment has been a subject of study and debate since it was first performed by Thomas Young in 1801. Over time, our understanding of the experiment has evolved, leading to the development of quantum mechanics and the wave-particle duality theory. New variations of the experiment have been conducted, providing further evidence and insights into the behavior of particles at the quantum level.

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