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  4. Investigation on diffraction of light
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Investigation on diffraction of light

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Offline hamdani yusuf (OP)

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Re: Investigation on diffraction of light
« Reply #100 on: 15/12/2023 02:54:34 »
Quote from: Origin on 14/12/2023 15:13:41
On all of these questions you ask, have you ever gotten an answer that you accepted?  My guess is no.  I'll have just assume the answer is no since this thread is now on ignore.
What's your answer to my question below?
Quote from: hamdani yusuf on 14/12/2023 13:50:49
Quote
Video showing single slit diffraction of a laser as the slit width is adjusted.  Suitable for A-Level Physics.

Let's focus on a single point in the center of the bright pattern on the screen. When the slit is narrow, this spot becomes much dimmer compared to when the slit is wider, even though the ray of light can still go directly from the light source to that specific spot on the screen.

It could mean that the opaque materials that the single slit apparatus is made of have blocked some of the light that initially would go to that central spot.
Or the edges of the slit have deflected the ray of light hitting them to the central spot, and produce partially destructive interference with the direct ray of light to that spot.
Or a combination of both.

Is there a way to determine which case is the most correct interpretation?
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Offline hamdani yusuf (OP)

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Re: Investigation on diffraction of light
« Reply #101 on: 18/12/2023 22:11:57 »
This simple experiment shows that light takes a definitive path during diffraction and interference.
« Last Edit: 22/12/2023 09:48:57 by hamdani yusuf »
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Offline hamdani yusuf (OP)

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Re: Investigation on diffraction of light
« Reply #102 on: 31/12/2023 13:24:47 »
Professional variable slit aperture is quite expensive. This is an affordable alternative using 2 pencils.
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Offline hamdani yusuf (OP)

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Re: Investigation on diffraction of light
« Reply #103 on: 31/12/2023 13:52:40 »
I've just recorded a variation of needle diffraction. In this version, the "needle" model is elongated in the direction of light propagation. It can be done using a name card, with the thickness around a half millimeter. Interestingly, the width of central bright spot in the interference pattern it produced is the same as the side spots. Instead of twice as wide like in a normal needle diffraction or single slit experiment.
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Offline hamdani yusuf (OP)

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Re: Investigation on diffraction of light
« Reply #104 on: 01/01/2024 12:15:06 »
Quote from: hamdani yusuf on 31/12/2023 13:52:40
I've just recorded a variation of needle diffraction. In this version, the "needle" model is elongated in the direction of light propagation. It can be done using a name card, with the thickness around a half millimeter. Interestingly, the width of central bright spot in the interference pattern it produced is the same as the side spots. Instead of twice as wide like in a normal needle diffraction or single slit experiment.
I've also recorded its Babinet's equivalent, which is thick single slit experiment. The result is more like a normal single slit experiment, where the central bright spot is twice as wide as the side spots. I think I'll compile them in a single video to show the comparison.
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Offline hamdani yusuf (OP)

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Re: Investigation on diffraction of light
« Reply #105 on: 03/01/2024 10:24:23 »
Here's the video.
Investigation on Diffraction of Light 26: Deep Single Slit and Wire
Quote
This video compares the result of diffraction and interference pattern from a deep single slit experiment and a thick single wire experiment. It explores the effects of depth or thickness of the aperture to the diffraction and interference pattern which is rarely discussed elsewhere.
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Offline hamdani yusuf (OP)

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Re: Investigation on diffraction of light
« Reply #106 on: 05/01/2024 04:10:30 »
When I googled "single slit experiment", this link shows up as the first answer.
Quote
In a single slit experiment, an alternating dark and bright pattern can be seen when light is imposed on a slit with a size corresponding to the wavelength of light. The only differences between a single slit and a double-slit experiment are the diffraction patterns and the intensity graphs.
https://www.inspiritvr.com/single-slit-diffraction-study-guide/#:~:text=In%20a%20single%20slit%20experiment%2C%20an%20alternating%20dark%20and%20bright,patterns%20and%20the%20intensity%20graphs.
Quote
What is Diffraction?
The process of bending light around corners such that it spreads out and illuminates regions where a shadow is anticipated is known as diffraction of light. In general, because both occur concurrently, it is difficult to distinguish between diffraction and interference. The diffraction of light is what causes the silver line we see in the sky. A silver line appears in the sky as the sunlight penetrates or strikes the cloud.

What Is Single Slit Diffraction?
The curving of light waves around a tight turn of an obstacle or an opening is known as the diffraction of light.
The single slit diffraction?s meaning is that an alternating dark and bright pattern can be seen when light is imposed on a slit with a size corresponding to the wavelength of light.
When light strikes the gap, secondary wavelets form at each point, as per Huygens? rule.
These wavelets start out in a phased manner and then disperse on all sides.
Each one of them covers a specific path to reach any location on the screen.
Due to the path difference, they reach diverse phases and may interact either constructively or destructively.

Single Slit Diffraction Formula

There are many weaknesses in the explanation above, but at least it correctly acknowledge that diffraction and interference are two distinct phenomena which often occur concurrently. There are sources which incorrectly declare that they are the same physical phenomenon, distinguished only by the number of slits involved.

Huygens? rule is commonly used to explain the diffraction-interference pattern produced by single slit experiment. It coincidentally matches with the standard setup. But more evidences are keep coming up contradicting the explanation using some variation of the experimental setup, e.g.
- Horizontally tilted diffraction.
- Vertically tilted diffraction.
- Non-diffractive slit using total internal reflection as the obstacle.
- Diffraction by polarizing obstacle.
- Diffraction by thick wire.

How many more evidence is required to convince us that we need a new explanation to replace Huygen's rule for explaining single slit experiment?
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Offline hamdani yusuf (OP)

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Re: Investigation on diffraction of light
« Reply #107 on: 29/01/2024 06:22:56 »
Quote from: hamdani yusuf on 05/01/2024 04:10:30
There are many weaknesses in the explanation above,
The most obvious one that I suspected right away is from multiple slit experiment. The more numbers of slit produce thinner bright spots. When there are infinitely many slits involved like what's explained in many sources, the bright spots should be infinitely thin. But that's not what we observe.
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Re: Investigation on diffraction of light
« Reply #108 on: 29/01/2024 16:43:38 »
Quote from: hamdani yusuf on 29/01/2024 06:22:56
The most obvious one that I suspected right away is from multiple slit experiment. The more numbers of slit produce thinner bright spots. When there are infinitely many slits involved like what's explained in many sources, the bright spots should be infinitely thin. But that's not what we observe.
Really?  When have observed the experiment with an infinite number of slits?
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Re: Investigation on diffraction of light
« Reply #109 on: 29/01/2024 16:51:24 »
Quote from: hamdani yusuf on 15/12/2023 02:54:34
What's your answer to my question below?
"Is there a way to determine which case is the most correct interpretation?"
Unfortunately there is no interpretation that you would accept, for some reason you never come to a conclusion, you just continue to ask the same question over and over ad nauseam.
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Offline hamdani yusuf (OP)

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Re: Investigation on diffraction of light
« Reply #110 on: 30/01/2024 06:08:00 »
Quote from: Origin on 29/01/2024 16:43:38
Quote from: hamdani yusuf on 29/01/2024 06:22:56
The most obvious one that I suspected right away is from multiple slit experiment. The more numbers of slit produce thinner bright spots. When there are infinitely many slits involved like what's explained in many sources, the bright spots should be infinitely thin. But that's not what we observe.
Really?  When have observed the experiment with an infinite number of slits?

Read the analysis in https://www.thenakedscientists.com/forum/index.php?topic=66301.msg719198#msg719198
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Re: Investigation on diffraction of light
« Reply #111 on: 30/01/2024 06:10:55 »
Quote from: Origin on 29/01/2024 16:51:24
Quote from: hamdani yusuf on 15/12/2023 02:54:34
What's your answer to my question below?
"Is there a way to determine which case is the most correct interpretation?"
Unfortunately there is no interpretation that you would accept, for some reason you never come to a conclusion, you just continue to ask the same question over and over ad nauseam.

I accept explanations that are not contradicted by experimental results. It's possible that more than one distinct explanations produce the same result for an experiment. But with more experiments some of them may start to fail.

You keep saying that they are well understood, without showing your own understanding about them.
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Re: Investigation on diffraction of light
« Reply #112 on: 31/01/2024 00:09:32 »
I'm planning to make another experiment in diffraction of light. I call it double layer single slit diffraction.
But I think I'll only do it after finishing the other experiment in progress, which uses electrohydrodynamic balance.
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Re: Investigation on diffraction of light
« Reply #113 on: 21/02/2024 02:46:43 »
Quote from: alancalverd on 20/02/2024 09:03:43
If it has a finite thickness, it isn't an edge, so you need an infinite number of Huygens constructions to predict the outcome. Better to simply note that as n→∞   so the diffraction pattern becomes less intense and more diffuse than two classic single-ray plots.

If you want to have more detailed technical discussion about diffraction of light, let's do it here.
What prevents the wavelets from bending toward the left side of the boundary between reflective and transparent surface?



* Screenshot 2024-02-21 094201.png (89.29 kB, 747x597 - viewed 704 times.)
« Last Edit: 21/02/2024 02:49:17 by hamdani yusuf »
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Offline hamdani yusuf (OP)

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Re: Investigation on diffraction of light
« Reply #114 on: 25/02/2024 16:13:04 »
Quote from: hamdani yusuf on 30/01/2024 06:10:55
I accept explanations that are not contradicted by experimental results. It's possible that more than one distinct explanations produce the same result for an experiment. But with more experiments some of them may start to fail.
Quote from: hamdani yusuf on 05/01/2024 04:10:30
Huygens? rule is commonly used to explain the diffraction-interference pattern produced by single slit experiment. It coincidentally matches with the standard setup. But more evidences are keep coming up contradicting the explanation using some variation of the experimental setup, e.g.
- Horizontally tilted diffraction.
- Vertically tilted diffraction.
- Non-diffractive slit using total internal reflection as the obstacle.
- Diffraction by polarizing obstacle.
- Diffraction by thick wire.

How many more evidence is required to convince us that we need a new explanation to replace Huygen's rule for explaining single slit experiment?
Some of you may get bored that I keep mentioning my experimental results regarding diffraction of light. I think it's necessary because some people keep forgetting about them, and go on making comments as if they don't exist.
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Offline hamdani yusuf (OP)

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Re: Investigation on diffraction of light
« Reply #115 on: 10/04/2024 12:44:12 »
The use of those lenses caused the light beam to be no longer parallel. It makes position of the aperture has significant impact on the interference patterns.
At 0:20 ten pinholes can produce interference patterns similar to diffraction grating. I'm curious what we'll get with just two pin holes.
« Last Edit: 11/04/2024 14:29:53 by hamdani yusuf »
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Re: Investigation on diffraction of light
« Reply #116 on: 27/04/2024 15:15:58 »
Fraunhofer Diffraction Explained
Quote
In this video, I describe the process of Fraunhofer diffraction (also known as far-field diffraction) in terms of the Fourier Transform and Fourier Optics. I go over the assumptions that underlie Fraunhoffer diffraction (both the paraxial approximation and the small-aperture approximation), and give the mathematical form that it takes.

This is part of my graduate series on optoelectronics / photonics, and is based primarily on Coldren's book on Lasers as well as graduate-level coursework I have taken in the EECS department at UC Berkeley.

Quote
In this video, I go over one-dimensional single-slit Fraunhofer diffraction. I walk through the mathematics using the Fourier Transform to calculate the intensity at a screen a distance d away, as a function of the screen coordinates.

You can have a perfectly valid mathematical model. But to be useful, it should reproduce observed experimental results without excessive ad hoc assumptions.
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Re: Investigation on diffraction of light
« Reply #117 on: 28/04/2024 08:47:37 »
https://youtube.com/shorts/nsxJQr57_is?feature=shared

What makes it different from single slit experiment?
What's the criteria to produce dark central spot?
« Last Edit: 28/04/2024 09:21:59 by hamdani yusuf »
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Re: Investigation on diffraction of light
« Reply #118 on: 01/05/2024 17:13:30 »
Fraunhofer

Fresnel

The experimental setup in the videos above seem only differ in the use of lens.
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Re: Investigation on diffraction of light
« Reply #119 on: 26/07/2024 06:52:27 »
Quote from: hamdani yusuf on 05/01/2023 05:21:28
Quote from: hamdani yusuf on 11/06/2022 14:04:23
I just got an even stronger evidence that diffracted light is produced by the edges of the obstacle, instead of the space between those edges. The experiment involves linear polarization.
I've finally uploaded the video.
Ijust got an idea extending the original question from diffraction by polarizing obstacles.
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