[hamdani yusuf (OP)]

Then why doesn't it say so?

Perhaps it assumes that the statement is simple enough for laypersons to understand what it means.

[alancalverd]

One of the problems with physics is that lay persons and journalists don't understand the difference between  strength, power, force and energy, so they go on to talk nonsense about a zero-carbon economy and other such drivel. The statement that an aperture can cast a shadow is worthy of a politician, not a scientist.

[hamdani yusuf (OP)]

Feynman has come from heaven to answer your question! Listen to him:

No one has ever been able to define the difference between interference and diffraction satisfactorily. It is just a quest of usage, and there is no specific, important physical difference between them. The best we can do is, roughly speaking, is to say that when there are only a few sources, say two interference sources, then the result is usually called interference, but if there is a large number of them, it seems that the word diffraction is more often used.1

To be more explicit read this passage from Ajoy Ghatak:

We should point out that there is not much of a difference between the phenomenon of interference and diffraction, indeed, interference corresponds to the situation when we consider the superposition of waves coming out from a number of point sources and diffraction corresponds to the situation when we consider waves coming out from an area sources like a circular or rectangular aperture or even a large number of rectangular apertures (like the diffraction grating). 2
Credits: 1 Feynman Lectures on Physics 2Optics-Ajoy Ghatak.

IMO, the confusion came from the lack of willingness and courage of science communicators and educators to make corrections when the errors were made by prominent or famous people that they highly respected. The quoted statements don't seem to reflect what Feynman believed to be the correct definitions of diffraction and interference, but rather an observation of how people in his time used those words.

[alancalverd]

Ghatak is as wrong as Feynman! He seems to base his definition of diffraction on diffraction gratings  (devices that exploit diffraction) rather than the single edge case (which is the underlying phenomenon) and an implicit belief that Huygens is a fact rather than a model.

[hamdani yusuf (OP)]

Reflection, Refraction, and Diffraction
Diffraction section starts at 9:20

[hamdani yusuf (OP)]

Diffraction: Why Does It Happen? (Physics Explained for Beginners)

Why do waves bend around objects or when passing through slits? Why does diffraction occur?

Timestamps:
00:00 - Intro
01:13 - What is Diffraction?
02:56 - Huygens' Wavelets Model for the Motion of Waves
04:29 - Wave Interference
07:37 - How Huygens' Model Works (and Explains Diffraction!)
11:24 - Problems with Huygens' Model
12:04 - How Fresnel Modified Huygens' Model (Huygens-Fresnel Principle)
14:36 - Announcement!

Hey guys, I'm back with another video, one which has been requested by a few of you! In this video I discuss a way in which you can VISUALISE how diffraction occurs. Hopefully after watching this video, you'll be able to understand why waves behave in such a strange way when passing through slits or when passing around objects, rather than just accepting that they do.

Of course, I need to make a disclaimer that the scientific models I discuss in this video (Huygens' Wavelets and the Huygens-Fresnel Principle) aren't necessarily how waves actually behave in real life - they're just really good mathematical models that accurately predict how waves behave in real life. But then, that's true of the majority of physics anyway.

Christiaan Huygens came up with a fairly simple but very clever way of understanding wave behaviour by breaking up waves into lots of small chunks that all behave in a very predictable way - by emitting lots of "secondary" waves. His model helped scientists to understand and visualise that waves must indeed bend in a very specific way when passing through a slit, or around an object. The idea that each point along a wave acts as a source of secondary waves, along with the idea that each of these secondary waves interferes with each other secondary wave it interacts with, accounted for a large chunk of observed wave behaviour.

For this reason, I wanted to show you Huygens' model, as well as talk about wave interference. For those of you who don't know about interference, and aren't happy with the pretty speedy and simplistic explanation I gave in this video, I highly suggest you check out the wikipedia page on interference. It's an idea often taught at high school (or college) level physics and it's mega interesting.

Huygens' model, genius though it was, had a few flaws. When we say flaws, what we really mean is that the model's predictions did not perfectly match what we observe in real life. So Jean-Augustin Fresnel came along and modified the model to make sure its predictions did match observed phenomena. Fresnel added an "obliquity factor" to the secondary waves emitted by each point, a sort of attenuation or "strength" factor depending on which direction these secondary waves were travelling in, as well as modifying the phases of the waves moving in each direction from a point source. These modifications to Huygens' original model naturally meant that Fresnel had created a new model entirely. This model is known as the Huygens-Fresnel Principle.

This is pretty good introduction to diffraction, which avoids confusion with interference.

Although it still needs fudge factors to make calculation matches with observation. It also hasn't covered non-diffractive edge and polarizing edge.

[hamdani yusuf (OP)]

I just got access to Claude 3.5 Sonnet and tested it for a while. I asked some questions about various things. It generally can answer well about general knowledge which can be found on textbooks. But it often gave wrong answers when the questions aren't widely known or addressed in standard  textbooks. Other AI models I compared with also gave similar results.

As usual, when I get access to a new AI model, I  check its understanding of topics I'm interested in. One of the most often question I asked is about diffraction.
When I asked basic questions about diffraction and interference, it's basically reciting textbooks or encyclopedia about it. But when I asked about less common questions, it seems to hallucinate a lot. Those questions are:
- single edge diffraction.
- horizontally tilted diffraction.
- vertically tilted diffraction.
- triple edges diffraction.
- diffraction by the edge of polarizing filter.
- non-diffractive edge.
It seems like it tried to fill the gap in its knowledge about the subject, and extrapolated too far from its training data.

[alancalverd]

I recently bought  a load of turf to make a new lawn. Common sense, and the contractor who supplied it, says you should water new turf every day until the roots grow into the underlying soil, but The Boss asked a chatbot which produced a range of answers including "let it dry out completely". 

Artificial,? yes. Intelligence? no. It's just GIGO on an industrial scale.

[paul cotter]

AI=artificial ignorance.

[hamdani yusuf (OP)]

Given adequately accurate training data, this AI model can exceed the performance of human expert in their field of expertise. Its failure in this topic can be blamed at least partially to the lack of good training data.
Future AI will have access to physical objects, and they will be able to verify or falsify their own existing beliefs. Before then, they depend on humans to provide good quality data, which is demonstrably lacking in this topic.

[paul cotter]

Agreed. A major proportion of this thread consists of poor quality human input.

[hamdani yusuf (OP)]

Agreed. A major proportion of this thread consists of poor quality human input.

They represent the most commonly accessed online sources that people get from search engines. Specific cases I asked AI chatbots that they failed to answer are rarely mentioned in those sources.

[alancalverd]

Given adequately accurate training data,

And how is the accuracy/relevance/consistency/credibility of the training data assessed? How much of it originated in a Russian spam factory?

At best, if we can magically filter out absurd, inaccurate, hysterical or deliberately malicious inputs, AI represents current human consensus. Advancing understanding or business success is all about challenging consensus. So AI is at best useless and at worst misleading.

[varsigma]

As usual, when I get access to a new AI model, I  check its understanding of topics I'm interested in.

AI with large-language models does not "understand" a subject. It is good at suggesting what words might be relevant and is trained to assemble meaningful sentences. That's about all it can do, search a large database which is a kind of dictionary, and string words together. It will make things up to try to impress you. (Ask that lawyer who lost their licence).

See if you can get one to understand French.

[hamdani yusuf (OP)]

As usual, when I get access to a new AI model, I  check its understanding of topics I'm interested in.

AI with large-language models does not "understand" a subject. It is good at suggesting what words might be relevant and is trained to assemble meaningful sentences. That's about all it can do, search a large database which is a kind of dictionary, and string words together. It will make things up to try to impress you. (Ask that lawyer who lost their licence).

See if you can get one to understand French.

Newer AI models are not limited to LLM. They combine whatever models work best for different use cases. That's why they need huge computational power to train. And they are growing exponentially.
I highlight the recent breakthroughs in AI, which I posted in my other thread.

6. Future directions:
   - Exploring more efficient training methods, like Microsoft's SLMs (small language models).
  - Decoupling reasoning from factual knowledge.
   - Potential for open-source models to facilitate experimentation.

What does it take for something to understand anything? Can animals understand something?
Can Neanderthals or other hominids understand something? Can aliens understand something?
Can children understand something? What about brainoid which can play Doom?

[hamdani yusuf (OP)]

Given adequately accurate training data,

And how is the accuracy/relevance/consistency/credibility of the training data assessed? How much of it originated in a Russian spam factory?

At best, if we can magically filter out absurd, inaccurate, hysterical or deliberately malicious inputs, AI represents current human consensus. Advancing understanding or business success is all about challenging consensus. So AI is at best useless and at worst misleading.

I just asked it for the source it used to answer my questions in this topic.

I apologize, but I don't have a specific source that I used to answer your questions on this topic. As an AI language model, I don't actually access external sources or databases in real-time. My responses are generated based on the training data I was exposed to during my development, which includes a wide range of scientific and educational materials on physics and optics. However, this training data has a cutoff date and I don't have access to the most recent research or publications.
For the most up-to-date and authoritative information on these topics, especially on advanced concepts like non-diffractive edges, I would recommend consulting recent peer-reviewed scientific journals, university-level physics textbooks, or speaking with experts in the field of optics.
If you're looking for reliable sources on these topics, some good starting points might include:

Optics textbooks by authors like Eugene Hecht or Frank L. Pedrotti
Journal articles from publications like Optics Express or Applied Optics
Online resources from reputable institutions like MIT OpenCourseWare or the Optical Society of America

For the most current research, especially on topics like non-diffractive edges, searching recent publications in scientific databases would be advisable.
I apologize if any of my responses contained inaccuracies or outdated information. It's always best to verify important information with current, peer-reviewed sources.

[hamdani yusuf (OP)]

Here's my further conversation with Claude 3.5 Sonnet.

do you know that shining a laser beam to a vertically tilted diffraction grating produces a circular pattern?

I apologize, but I need to correct a misunderstanding in your statement. Shining a laser beam on a vertically tilted diffraction grating does not typically produce a circular pattern. Let me explain the actual behavior:

Standard diffraction grating pattern:

When a laser beam hits a diffraction grating perpendicular to its surface, it produces a linear pattern of diffraction orders.


Effect of vertical tilt:

Tilting the grating vertically will cause the diffraction pattern to rotate.
The pattern remains linear but is no longer horizontal.
As the tilt angle increases, the pattern rotates further from the horizontal.


Conical diffraction:

At very large tilt angles, the diffraction pattern can form a cone.
This is known as conical diffraction.
However, the pattern on a flat screen would appear as a conic section (e.g., hyperbola), not a circle.


Circular patterns in diffraction:

Circular patterns are typically associated with other optical setups, such as:
a) Diffraction from circular apertures (Airy disk)
b) Zone plates
c) Certain types of crystal diffraction


Possible misconception:

The observation of a circular pattern might be due to other factors in the experimental setup or a misinterpretation of the observed pattern.



If you've observed a circular pattern in such an experiment, it would be worth examining the setup carefully to identify the source of this unexpected result. It could be due to additional optical elements, the nature of the light source, or other factors in the experimental arrangement.
Thank you for bringing this up. It's an excellent opportunity to clarify the behavior of diffraction gratings under different conditions. Would you like to discuss this further or explore other aspects of diffraction grating behavior?

Tell me more about conical diffraction in vertically tilted diffraction grating

Certainly! Conical diffraction in a vertically tilted diffraction grating is a fascinating phenomenon. Let's delve deeper into this topic:

Basic concept:

Conical diffraction occurs when a diffraction grating is tilted significantly out of the plane perpendicular to the incident light.
The diffracted light forms a cone around the grating normal, rather than lying in a single plane.


Mechanism:

As the grating is tilted vertically, the diffraction orders move out of the horizontal plane.
At large tilt angles, the orders form a cone-shaped pattern in three-dimensional space.


Cone angle:

The angle of the cone depends on the grating period, wavelength of light, and tilt angle.
It can be described by the equation: cos(φ) = cos(θi)cos(θd) - sin(θi)sin(θd)cos(α),
where φ is the cone angle, θi is the incident angle, θd is the diffraction angle, and α is the tilt angle.


Observed pattern:

On a flat screen, the pattern appears as conic sections:

Circle (if screen is perpendicular to cone axis)
Ellipse, parabola, or hyperbola (depending on screen orientation)




Order distribution:

Different diffraction orders appear at different points along these conic sections.


Wavelength dependence:

For polychromatic light, each wavelength forms its own cone, leading to complex spectral patterns.


Applications:

Spectroscopy: Used in some specialized spectrometers for unique dispersion patterns.
Beam shaping: Can be used to create specific light distributions.
Optical sensing: The unique patterns can be used in certain sensing applications.


Historical significance:

First predicted theoretically by William Rowan Hamilton in 1837.
Later observed experimentally in biaxial crystals.


Comparison to in-plane diffraction:

Offers more degrees of freedom in manipulating light.
Can access diffraction geometries not possible with traditional in-plane setups.


Challenges in analysis:

Requires more complex mathematical treatment than standard grating diffraction.
Often necessitates 3D modeling for accurate predictions.



This phenomenon demonstrates the rich behavior of light when interacting with periodically structured materials in non-standard geometries. It's a great example of how tilting a simple optical element can lead to complex and useful optical effects.

[hamdani yusuf (OP)]

Then I followed up with the next question, is conical diffraction also found in vertically tilted single slit aperture?

Your question touches on an interesting aspect of diffraction phenomena. Let me explain the relationship between conical diffraction and a vertically tilted single slit aperture:

Conical diffraction in single slits:

Strictly speaking, true conical diffraction as observed in gratings does not occur in a single slit aperture.
Conical diffraction requires a periodic structure (like a grating) to produce the distinctive cone-shaped diffraction pattern.


Single slit diffraction pattern:

When a single slit is vertically tilted, the diffraction pattern does change, but not in the same way as a grating.
The pattern remains essentially in one plane, rather than forming a cone.


Effect of vertical tilt on single slit:

The main effect is a rotation of the diffraction pattern.
The central maximum and subsequent minima and maxima rotate in the plane perpendicular to the slit's long axis.


Differences from grating diffraction:

Single slit diffraction produces a continuous intensity distribution.
Gratings produce discrete diffraction orders, which form the conical pattern when tilted.


Similarities in mathematical treatment:

While not conical, the tilted single slit can be analyzed using similar mathematical approaches, considering the change in effective slit width.


Three-dimensional considerations:

At extreme tilt angles, the single slit pattern does become three-dimensional, but it's better described as a fan-shaped pattern rather than conical.


Practical implications:

The tilted single slit is often used in studies of diffraction fundamentals.
It's less commonly used in applications requiring specific spectral dispersion, where gratings are preferred.


Fresnel vs. Fraunhofer diffraction:

Tilting can affect whether the observed pattern is in the Fresnel or Fraunhofer regime, depending on the geometry.



In summary, while a vertically tilted single slit does produce interesting diffraction effects, it doesn't exhibit true conical diffraction. The pattern changes are more straightforward, primarily involving rotation and some distortion of the familiar single-slit diffraction pattern.

[alancalverd]

How sad, that people have spent entire careers developing software that can't ignore a meaningless question!

Define "vertical", please.

[hamdani yusuf (OP)]

at right angles to a horizontal plane; in a direction, or having an alignment, such that the top is directly above the bottom.
Google.