[hamdani yusuf (OP)]

You have made the usual textbook errors of assuming Huygens' infinite array of spherical wavelets  then attempting to represent it with ray propagation of truncated wavefronts.

Is there unusual textbook that doesn't make the same error?

[hamdani yusuf (OP)]

Yes, because it does.

As I've shown, it predicts diffraction.

How do you explain half interference pattern that I have shown in another thread?

In case you are wondering which one.

Frequently. I  am a physicist.

It looks like we are lucky to have a physicist on board. I'd like to hear what you think about this problem.
Or may be you know someone who is more suitable to give an answer.

Apologies for picking this up so late in the discussion. Please remind me which problem? 

Here. See the pattern shown in 0:07. Do you have a better explanation?

Here's my newest video investigating diffraction of light by producing single side interference pattern.

[alancalverd]

Do you know Lloyd's mirror?

Wikipedia gives a good summary buut rather overcooks it, I feel:

The Lloyd mirror effect has been implicated as having an important role in explaining why marine animals such as manatees and whales have been repeatedly hit by boats and ships. Interference due to Lloyd's mirror results in low frequency propeller sounds not being discernible near the surface, where most accidents occur.

Manatees and whales are mammals so come to the surface to breathe, and also to catch pelagic prey. Ships are also mostly on the surface. Where else could they possibly collide?

But I digress. The ray construction shows that photons can arrive at a given point via two different path lengths, but doesn't imply interference because it would be equally applicable to particles as to waves. There is no mechanism for the destructive interference of particles.

[alancalverd]

Is there unusual textbook that doesn't make the same error?

I haven't looked very hard, but I doubt it.

[hamdani yusuf (OP)]

Do you know Lloyd's mirror?

Wikipedia gives a good summary buut rather overcooks it, I feel:

The Lloyd mirror effect has been implicated as having an important role in explaining why marine animals such as manatees and whales have been repeatedly hit by boats and ships. Interference due to Lloyd's mirror results in low frequency propeller sounds not being discernible near the surface, where most accidents occur.

Manatees and whales are mammals so come to the surface to breathe, and also to catch pelagic prey. Ships are also mostly on the surface. Where else could they possibly collide?

But I digress. The ray construction shows that photons can arrive at a given point via two different path lengths, but doesn't imply interference because it would be equally applicable to particles as to waves. There is no mechanism for the destructive interference of particles.

Are you intentionally making simple things more complicated?

Just in case you can't find the correct link with the correct context.

https://en.wikipedia.org/wiki/Lloyd%27s_mirror

Lloyd's mirror is an optics experiment that was first described in 1834 by Humphrey Lloyd in the Transactions of the Royal Irish Academy.[1] Its original goal was to provide further evidence for the wave nature of light, beyond those provided by Thomas Young and Augustin-Jean Fresnel. In the experiment, light from a monochromatic slit source reflects from a glass surface at a small angle and appears to come from a virtual source as a result. The reflected light interferes with the direct light from the source, forming interference fringes.[2][3] It is the optical wave analogue to a sea interferometer.[4]

The reason I mentioned this experiment is to provide an example where interference occurs without involving diffraction, thus supporting the assertion that interference and diffraction are two distinct phenomena. They can occur at the same time in an experimental setup, but they can also occur independently.
In a Venn diagram, their relationship will look like this.

Commonly discussed single slit and double slit experiments are represented by the red area in the diagram.

[alancalverd]

The reason I mentioned this experiment is to provide an example where interference occurs without involving diffraction

I think we agreed on that a long while ago!

I also mentioned interference between independent but synchronised  radio sources used for long range navigation, and the problems caused by edge diffraction of a homing beacon, with no interference.

But the fact remains that mixing ray optics with wave models in a textbook can lead to some serious confusion.

[hamdani yusuf (OP)]

The reason I mentioned this experiment is to provide an example where interference occurs without involving diffraction

I think we agreed on that a long while ago!

I also mentioned interference between independent but synchronised  radio sources used for long range navigation, and the problems caused by edge diffraction of a homing beacon, with no interference.

But the fact remains that mixing ray optics with wave models in a textbook can lead to some serious confusion.

How do you explain Lloyd's mirror interference using Huygen's principle?
How do you calculate positions of destructive and constructive interference on the screen?

[alancalverd]

The same way that you explain calculate everything else to which Huygens applies.

I repeat for the nth time, Huygens is a mathematical model, not an explanation.

[hamdani yusuf (OP)]

The same way that you explain calculate everything else to which Huygens applies.

I repeat for the nth time, Huygens is a mathematical model, not an explanation.

Is it falsifiable?

[alancalverd]

Yes. All you have to do is conduct an experiment whose results are not correctly predicted by the Huygens model. Your report is eagerly awaited!

[hamdani yusuf (OP)]

Yes. All you have to do is conduct an experiment whose results are not correctly predicted by the Huygens model. Your report is eagerly awaited!

What does it predict, exactly?
Does it predict half interference pattern?
Does it predict polarized single slit diffraction?

[Bored chemist]

Yes. All you have to do is conduct an experiment whose results are not correctly predicted by the Huygens model. Your report is eagerly awaited!

What does it predict, exactly?
Does it predict half interference pattern?
Does it predict polarized single slit diffraction?

Do you really not understand that those questions were asked when Huygens put the idea forward and, if it hadn't worked, the idea would have been discarded?

[hamdani yusuf (OP)]

Yes. All you have to do is conduct an experiment whose results are not correctly predicted by the Huygens model. Your report is eagerly awaited!

What does it predict, exactly?
Does it predict half interference pattern?
Does it predict polarized single slit diffraction?

Do you really not understand that those questions were asked when Huygens put the idea forward and, if it hadn't worked, the idea would have been discarded?

Do you have any reference?
Should we take your words for granted?

[Bored chemist]

Yes. All you have to do is conduct an experiment whose results are not correctly predicted by the Huygens model. Your report is eagerly awaited!

What does it predict, exactly?
Does it predict half interference pattern?
Does it predict polarized single slit diffraction?

Do you really not understand that those questions were asked when Huygens put the idea forward and, if it hadn't worked, the idea would have been discarded?

Do you have any reference?
Should we take your words for granted?

So, that's a "No".
You do not understand how science works.

Have you considered learning?
You are asking me to find a published record of someone saying "yes, it still works".
Why would anyone bother to publish that?

I'm not asking you to take my word for anything.
I'm saying that, in the last 300 years or more, plenty of people* have compared the calculation with the experiments and found that Huygens' construction works (within it's field of applicability).

Because, if they had found that it didn't work they would be famous as "the guy who proved Huygens was wrong.".

Do you really not see that?

* and I mean clever people- not you and me.

[hamdani yusuf (OP)]

So, that's a "No".
You do not understand how science works.

How do you think science work? It looks like your understanding is different than mine.

[hamdani yusuf (OP)]

Have you considered learning?
You are asking me to find a published record of someone saying "yes, it still works".
Why would anyone bother to publish that?

I'm learning by asking question in a science forum, among other ways, such as making experiments and reading online resources.
In order to say "yes, it still works", there should be a record showing that it did work in the first time.

[hamdani yusuf (OP)]

I'm not asking you to take my word for anything.
I'm saying that, in the last 300 years or more, plenty of people* have compared the calculation with the experiments and found that Huygens' construction works (within it's field of applicability).

Some theories which survived for thousands years turned out to be false.
Everything works until it doesn't.
Have you watched Sal Khan's explanation on single slit experiment? Do you agree with him? Can you find something to improve the explanation?

[Bored chemist]

Some theories which survived for thousands years turned out to be false.

Not sure that's true of any scientific thory given that science has only been around for a few centuries.

But, more to the point.
Some calculations have been tested for 300 years and found to be true.
That group includes Huygens' construction.

[Bored chemist]

In order to say "yes, it still works", there should be a record showing that it did work in the first time.

There is
https://en.wikipedia.org/wiki/Treatise_on_Light

Did you not realise that?

[hamdani yusuf (OP)]

Because, if they had found that it didn't work they would be famous as "the guy who proved Huygens was wrong.".

Do you really not see that?

* and I mean clever people- not you and me.

They did find the weaknesses of Huygen's principle.
They are not famous because they can't show a better explanation.

Feynman defines the generalized principle in the following way:

"Actually Huygens’ principle is not correct in optics. It is replaced by Kirchoff’s [sic] modification which requires that both the amplitude and its derivative must be known on the adjacent surface. This is a consequence of the fact that the wave equation in optics is second order in the time. The wave equation of quantum mechanics is first order in the time; therefore, Huygens’ principle is correct for matter waves, action replacing time."
https://en.wikipedia.org/wiki/Huygens%E2%80%93Fresnel_principle#Generalized_Huygens'_principle

A simple Google search for limitations of Huygens' principle gives these answers.

The limitations of Huygens Wave Theory of Light are as follows:
It could not explain rectilinear propagation of light
It could not explain phenomenon of polarisation of light and phenomenon like Compton Effect, photoelectric effect.

https://www.toppr.com/ask/content/concept/drawbacks-of-huygens-wave-theory-210352/

Huygens’ principle failed to provide reasons for wave propagation in backward directions.The principle failed to explain the rectilinear propagation of light.It also failed to prove the concept of polarisation of light, emission of light, absorption of light, and the photoelectric effect. (Source: https://protonstalk.com/light/huygens-principle/#Limitations)
https://protonstalk.com/light/huygens-principle/#Limitations