[Bored chemist]

You seem to  have forgotten what you've said previously.

It only seems that way to you.
All the things I said are consistent with each other.
Do you understand that an aperture and an edge mean the same thing?
The only reason you have a beam of finite width is that something got in the way of light outside the beam.

Do you now accept that you were talking nonsense when you said

You seem to  have forgotten what you've said previously.

[hamdani yusuf (OP)]

You seem to  have forgotten what you've said previously.

It only seems that way to you.
All the things I said are consistent with each other.
Do you understand that an aperture and an edge mean the same thing?
The only reason you have a beam of finite width is that something got in the way of light outside the beam.

Do you now accept that you were talking nonsense when you said

You seem to  have forgotten what you've said previously.

It seems like edge is not the same as aperture, according to this wikipedia article.

In optics, an aperture is a hole or an opening through which light travels. More specifically, the aperture and focal length of an optical system determine the cone angle of a bundle of rays that come to a focus in the image plane.
https://en.wikipedia.org/wiki/Aperture

It's not the edges of the lens as you suggested.
How many edges do you consider when observing a standard single slit experiment using laser pointer?

[hamdani yusuf (OP)]

26 seconds into the first video you say that diffraction by a single edge can not be explained.

In fact, it can be explained (and modeled).
https://physics.stackexchange.com/questions/232254/how-to-calculate-a-straight-edge-diffraction-pattern

Here's a diagram shown in the link above.

This pattern can only appear with diverging light beam before hitting a diffractive edge. My experiment in
video #11 Non-parallel light source
shows this phenomenon.
Single edge diffraction of a narrow parallel light beam like an ordinary laser pointer doesn't produce interference pattern.

The pattern in single edge diffraction experiment shown in the diagram above looks more like diffraction of Non-parallel light source

Instead of parallel light source.

The rest of the video can be watched here

video #2 Edge shapes effect

video #3 Diffraction by transparent objects

[alancalverd]

#282 shows a very interesting graph, suggesting that, 1 m from the edge, 140% of the incident intensity appears 12 meters into the shadow area  and 100% is still present at 50m. Beyond Nikola Tesla's wildest dreams! The fringe spacing  of between 5m and 12 m seems remarkable considering the incident light wavelength is 0.0000005 m. I wonder what phenomenon is occurring here? 

[Bored chemist]

It seems like edge is not the same as aperture

Do you understand that you can't have one without the other?

[Bored chemist]

#282 shows a very interesting graph, suggesting that, 1 m from the edge, 140% of the incident intensity appears 12 meters into the shadow area  and 100% is still present at 50m.

Yes.
It's interesting,but not unexpected.

A diffraction pattern typically has light and dark areas.
But there's no mechanism for the light energy  to "disappear" from the dark areas.
The conservation of energy tells you it has to go somewhere.
Measurements tell you it goes into the bright areas which can be brighter than they would be without the effects of interference.

I think there are "problems" with the distances on that graph, but 140% brighter than you would expect is... just what you expect.

[hamdani yusuf (OP)]

It seems like edge is not the same as aperture

Do you understand that you can't have one without the other?

Every aperture has edge(s), but not the other way around.

Do you have something to say about my statements below?

From my experience, diffraction requires partial opacity/transparency. Perfectly opaque objects, as well as perfectly transparent objects don't produce observable diffraction.

I haven't found a published source mentioning the necessity of partial opacity/transparency of the obstacle to produce diffraction of light. Please let me know if I miss something.

[Bored chemist]

Perfectly opaque objects, as well as perfectly transparent objects don't produce observable diffraction.

Most people consider a ball bearing to be perfectly opaque to visible light.
https://en.wikipedia.org/wiki/Arago_spot

[hamdani yusuf (OP)]

#282 shows a very interesting graph, suggesting that, 1 m from the edge, 140% of the incident intensity appears 12 meters into the shadow area  and 100% is still present at 50m. Beyond Nikola Tesla's wildest dreams! The fringe spacing  of between 5m and 12 m seems remarkable considering the incident light wavelength is 0.0000005 m. I wonder what phenomenon is occurring here? 

Here's a diagram of knife edge diffraction-interference pattern, plotted on top of the photograph of an experiment.


And here are pictures of knife edge diffraction experiment.




What do you think is the cause of the difference?

[hamdani yusuf (OP)]

Perfectly opaque objects, as well as perfectly transparent objects don't produce observable diffraction.

Most people consider a ball bearing to be perfectly opaque to visible light.
https://en.wikipedia.org/wiki/Arago_spot

It's not perfectly opaque in visible light, especially at the edge.

[alancalverd]

The diffraction pattern now makes perfect sense - we are looking at interference between the primary beam and the diffracted light in the illuminated area. However the horizontal scale in the calculated graph you presented earlier is wrong by several orders of magnitude! The dangerous stuff actually occurs in the dark area, where a diffracted medium wave radio signal is detectable and appears to be coming from somewhere other than the transmitter. This can result in flying into a cliff or a mountain, thinking that the edge of the obstruction is actually the nondirectional homing beacon some miles away.

[Bored chemist]

Perfectly opaque objects, as well as perfectly transparent objects don't produce observable diffraction.

Most people consider a ball bearing to be perfectly opaque to visible light.
https://en.wikipedia.org/wiki/Arago_spot

It's not perfectly opaque in visible light, especially at the edge.

You are saying that light goes through hardened steel.
Do you have evidence of that?

[hamdani yusuf (OP)]

This is a video demonstrating Poisson's spot. The thumbnail is misleading, just used as a clickbait.

Notice that the light source used here has a wide beam when it hits the ball, thus lights up the whole circumference.

You won't find the Poisson's spot if you use a laser pointer with a light beam narrower than the ball.
You'll get a diffraction effect like what I've shown in edge shape effect video when the light beam only hits a small part of the ball's edge.

[hamdani yusuf (OP)]

The diffraction pattern now makes perfect sense - we are looking at interference between the primary beam and the diffracted light in the illuminated area. However the horizontal scale in the calculated graph you presented earlier is wrong by several orders of magnitude! The dangerous stuff actually occurs in the dark area, where a diffracted medium wave radio signal is detectable and appears to be coming from somewhere other than the transmitter. This can result in flying into a cliff or a mountain, thinking that the edge of the obstruction is actually the nondirectional homing beacon some miles away.

In the picture below, the diffracted light is only the small portion shown on the right side of the vertical axis. It's where the light beam goes to the area behind the obstacle.

The bright area on the left side with periodic dark stripes are the result of interference between the original wide beam light source and the light slightly deflected by the edge of the obstacle. It's an example of non-diffractive interference, which I discussed in another thread about common confusion between diffraction and interference.

Here's my video about non-diffractive interference.

[Bored chemist]

You won't find the Poisson's spot if you use a laser pointer with a light beam narrower than the ball.

Nobody said that you would.

Now, can we get back to this?

You are saying that light goes through hardened steel.
Do you have evidence of that?

[hamdani yusuf (OP)]

Most people consider a ball bearing to be perfectly opaque to visible light.

Steel is not perfectly opaque in visible light spectrum. It has penetration depth longer than the wavelength.

The depth of a ball is nearly zero at its edge.

[Bored chemist]

The depth of a ball is nearly zero at its edge.

At the edge it is exactly zero. But it gets thicker very quickly.
Are you saying that the Poisson spot is cause by light going through the metal?
Can you think of a simple way to test that?

[alancalverd]

So far this is all classical optics, from last century's textbooks. Is this discussion going anywhere in the direction of new theories?

[hamdani yusuf (OP)]

So far this is all classical optics, from last century's textbooks. Is this discussion going anywhere in the direction of new theories?

Considering how many misconceptions we can find online, my explanation for light can be said to be new for many of us. It's even new for myself. I was also misled by widely taught explanations in textbooks, especially involving Huygen's and Fermat's principles. I found no reference in quantum mechanics textbooks which decisively state the errors of those principles

[Bored chemist]

Considering how many misconceptions we can find online,

Like the idea that a meaningful amount of light will go through a steel ball bearing...