[alancalverd]

But light propagates through optical fiber slower than through air. Hence the speed is different.

Because ε and μ are different. What do you expect?

[Bored chemist]

Even a professional physicist can't explain refraction clearly.

This guy did.

[hamdani yusuf (OP)]

But light propagates through optical fiber slower than through air. Hence the speed is different.

Because ε and μ are different. What do you expect?

I expect he didn't write this.

In fact, they have the same speed, but different phase.

I hope you can learn something about context.

[Bored chemist]

I expect he didn't write this.

I'm sure he didn't write it; because I did.

I hope you can learn something about context.

The context is that I wrote it here.

He makes a statement about combining waves.
If you combine waves of different speeds you get other, slower waves.
This is true; but irrelevant.
At about 8:55 he says that you get a combination of waves in light travelling through matter.
He doesn't say how they differ. He doesn't say if they differ in phase or speed.
In fact, they have the same speed, but different phase.

He could certainly have made it clearer than he did.

[hamdani yusuf (OP)]

Even a professional physicist can't explain refraction clearly.

This guy did.

The explanation in the video is based on Feynman's Lecture. Yet, the video host was only recently get the intuitive explanation behind the details of math equations, even though he is a physics lecturer himself. Hence it doesn't seem like the standard explanation commonly given in mainstream physics class.

Somehow unscientific attitude was displayed here toward the video.

Have you seen the video?

No, the reason there is no need to see it is this statement you made:
"The explanation offered in this video is more compatible with my own experiments".

You are not physicist (probably haven't even taken a single physics course) and your posting history is full of errors and misconceptions, so if the video disagrees with mainstream physics and aligns with your ideas then it is not worth watching.

[hamdani yusuf (OP)]

I expect he didn't write this.

I'm sure he didn't write it; because I did.

I hope you can learn something about context.

The context is that I wrote it here.

He makes a statement about combining waves.
If you combine waves of different speeds you get other, slower waves.
This is true; but irrelevant.
At about 8:55 he says that you get a combination of waves in light travelling through matter.
He doesn't say how they differ. He doesn't say if they differ in phase or speed.
In fact, they have the same speed, but different phase.

He could certainly have made it clearer than he did.

The word "he" I wrote there refers to you, BC.
The word "you" I wrote there refers to Alan.

[hamdani yusuf (OP)]

This guy did.

There's a little problem in 16:40 time mark. It shows like the X-ray passing through the glass can reach the right side of the screen sooner than the X-ray passing through air.

A more reasonable explanation is that the X-ray phase is delayed more than half wave, creating an illusion that it was sped up less than a half wave. Hence, actually the X-ray propagates through glass even slower than ultraviolet light, which is slower than visible light.

[Bored chemist]

A more reasonable explanation is that the X-ray phase is delayed more than half wave, creating an illusion that it was sped up less than a half wave. Hence, actually the X-ray propagates through glass even slower than ultraviolet light, which is slower than visible light.

That may be reasonable, but it doesn't work.
It's not a fixed phase delay, it's a delay each time the photon encounters an electron.
If your idea was right then the apparent refractive index would depend on thickness.

[hamdani yusuf (OP)]

A more reasonable explanation is that the X-ray phase is delayed more than half wave, creating an illusion that it was sped up less than a half wave. Hence, actually the X-ray propagates through glass even slower than ultraviolet light, which is slower than visible light.

That may be reasonable, but it doesn't work.
It's not a fixed phase delay, it's a delay each time the photon encounters an electron.
If your idea was right then the apparent refractive index would depend on thickness.

Don't calculate per electron. Do it accumulatively per wavelength penetration depth.

[alancalverd]

wavelength penetration depth.

That's a novel concept. Can you define and explain it? 

[Sheilataylor]

But light propagates through optical fiber slower than through air. Hence the speed is different.

Because ε and μ are different. What do you expect?

It seems this was obvious.

[hamdani yusuf (OP)]

wavelength penetration depth.

That's a novel concept. Can you define and explain it? 

Let's say that the wavelength of the X-ray is 10 Angstrom, and the atomic spacing of the glass is 1 Angstrom. The phase of the X-ray is delayed by 7 Angstrom after penetrating the glass as far as 10 Angstrom. It creates an illusion that the phase is sped up by 30%. In average, each atomic layer of the glass delays the phase by 0.7 Angstrom.

[Bored chemist]

Don't calculate per electron. Do it accumulatively per wavelength penetration depth.

We do.
That was my point.

[hamdani yusuf (OP)]

Don't calculate per electron. Do it accumulatively per wavelength penetration depth.

We do.
That was my point.

If your idea was right then the apparent refractive index would depend on thickness.

The apparent refractive index would depend on thickness only if the glass is thinner than the wavelength of X-ray, which is impractical.

[Bored chemist]

A more reasonable explanation is that the X-ray phase is delayed more than half wave,

When?
is it half a wave at every interaction with an electron?
Half a wave for every millimetre of glass?

[hamdani yusuf (OP)]

A more reasonable explanation is that the X-ray phase is delayed more than half wave,

When?
is it half a wave at every interaction with an electron?
Half a wave for every millimetre of glass?

Let's say that the wavelength of the X-ray is 10 Angstrom, and the atomic spacing of the glass is 1 Angstrom. The phase of the X-ray is delayed by 7 Angstrom after penetrating the glass as far as 10 Angstrom. It creates an illusion that the phase is sped up by 30%. In average, each atomic layer of the glass delays the phase by 0.7 Angstrom.

[Deecart]

Why do we still have widely spread incorrect explanations as described in the first videos here?

The answer is straight forward.
Because we only provide explainations based on theory, not some proof based on some experimentation.
If there was some experimental proof, any physicist would, like everytime, use these experiments to explain the phenomenon.

Here, when we say that the light wave produce a change in the electronic situation of the matter, this is theory.
To proof that is is the case (so using some experiment) we would need to do the observation that there is a delay between the advance of the wave into the matter and the feedback effect.
So we have to do the observation to give the proof : When the firsts photons enter the matter, the light beam go straight and when the electron of the matter is affected by the beam (after some delay), the light beam do not go straight away any more, so it "curves".

 

[hamdani yusuf (OP)]

Why do we still have widely spread incorrect explanations as described in the first videos here?

The answer is straight forward.
Because we only provide explainations based on theory, not some proof based on some experimentation.
If there was some experimental proof, any physicist would, like everytime, use these experiments to explain the phenomenon.

Here, when we say that the light wave produce a change in the electronic situation of the matter, this is theory.
To proof that is is the case (so using some experiment) we would need to do the observation that there is a delay between the advance of the wave into the matter and the feedback effect.

I've mentioned many times previously, behaviors of electromagnetic waves can be better observed in longer wavelength where the size and shape of the antenna can be easily measured and visualized. By accepting that visible light and X-rays are simply electromagnetic wave with shorter wavelength, we can deduce the internal structure of the materials interacting with them.

Continuing my effort to understand the behavior of microwave in another thread, here I'd like to share experiments showing how radio wave behaves. I've prepared some experimental equipment, but didn't have enough time to execute the experiments yet, so for now I'll put this well made video from Harvard Natural Sciences Lecture Demonstrations first.

So we have to do the observation to give the proof : When the firsts photons enter the matter, the light beam go straight and when the electron of the matter is affected by the beam (after some delay), the light beam do not go straight away any more, so it "curves".

Where does it curve to?
How does it return to the original direction?
Have you watched the first video in this thread?

[Deecart]

Where does it curve to?

It do the refraction we are talking about (refraction = curving).

How does it return to the original direction?

It do not return to the previous direction.
It start with no refraction at all (because there are no photon already at place so the electrons are not already affected) : So the light beam go first straight away. THEN, with some delay, the light beam "curve" (do the refraction).
This is what we should see if the theorical explaination in the video is correct.

Have you watched the first video in this thread?

Yes.

[hamdani yusuf (OP)]

It do not return to the previous direction.
It start with no refraction at all (because there are no photon already at place so the electrons are not already affected) : So the light beam go first straight away. THEN, with some delay, the light beam "curve" (do the refraction).
This is what we should see if the theorical explaination in the video is correct.

How do the light know where to curve?
After initial bent on the interface of different media, the light goes in the straight line again. When exiting the refractive medium, the light goes back to the original direction if the front and rear surfaces are parallel.

Yes.

The video debunks your explanation, besides some others.