[alancalverd]

A "particle" that is everywhere all the time isn't very particulate, is it?

But a particle that could be anywhere at any time but only interacts at one point and one time, is neatly described by  Schrodinger and Planck, properly understood.

[Petrochemicals]

A "particle" that is everywhere all the time isn't very particulate, is it?

But a particle that could be anywhere at any time but only interacts at one point and one time, is neatly described by  Schrodinger and Planck, properly understood.

Sounds like some sort of field that becomes activated somehow, producing a particle.

[alancalverd]

Lousy interpretation, a bit like "collapsing wavefunctions". Just adds confusion.

It's much easier to stick with the experimental observations: we generally need to model propagation with wave equations, and note that detection is better modelled at high photon energies (optical and above) with discrete quanta.

Anything else is philosophy, not physics.

I've never understood why people find this difficult, and have to introduce anthropocentric observer effects and other mysticisms. You can write down the probability function of the score from throwing n dice. There is a very low probability (1/n⁶) of scoring n or 6n  and a very high probability of scoring around 3.5n. That is a continuous Schrodinger-type predictive wave function, and gets more "continuous" as n  increases. When you throw the dice you will always and only get a single quantised integer score - a Planck result. If there was such a thing as an observer effect, you could make a fortune by asking everyone else to shut their eyes when the croupier rolls the dice.

[evan_au]

When you throw the dice you will always and only get a single quantised integer score

My high school geology teacher was preparing us for a field trip, and wanted to make a point about the way shells tend to lie when they die (as I recall).
He grabbed the curved plastic lens cap off his slide projector (imagining it like one side of a bivalve) and flipped it in the air. It bounced on the floor, and came to a stop, neatly balanced on the narrow rim. This was so spectacularly unlikely that I think the class entirely missed the point of the illustration...

[Eternal Student (OP)]

Hi.

There is a very low probability (1/n⁶) of scoring ...

   You did that deliberately didn't you?  I'm just to pretend I didn't see it and hope it reads   (1/6)ⁿ when I get back here.

Best Wishes.

[alancalverd]

Well spotted, Pike! Just testing to see if the troops were awake! Or am I getting old?

[Petrochemicals]

I was going to suggest the same, but can’t find an example of optical to microwave redshift. Haven’t had a lot of time, will give so e thought next week.

Lasers  can theoretical turn  microwave to photon, there are filters that can change infra red to blue, as seen in confinement  fusion.

[Bored chemist]

there are filters that can change infra red to blue, as seen in confinement  fusion.

Not really.

[hamdani yusuf]

What is the equation describing how a magnetic field is induced by a moving charge?

Ampere's Law.

https://en.wikipedia.org/wiki/Amp%C3%A8re%27s_circuital_law

In classical electromagnetism, Ampère's circuital law (not to be confused with Ampère's force law)[1] relates the integrated magnetic field around a closed loop to the electric current passing through the loop. James Clerk Maxwell (not Ampère) derived it using hydrodynamics in his 1861 published paper "On Physical Lines of Force"[2] In 1865 he generalized the equation to apply to time-varying currents by adding the displacement current term, resulting in the modern form of the law, sometimes called the Ampère–Maxwell law,[3][4][5] which is one of Maxwell's equations which form the basis of classical electromagnetism.

Where do you find electric charge or velocity in the article above?

[paul cotter]

Petro, there are no filters that can change the frequency of incident radiation. What I believe you are thinking about is certain crystals that perform frequency doubling operations such as infrared to visible, similar to the frequency doublers in common use in electronics. A lot of visible lasers generate at infrared and then double up to visible.

[alancalverd]

Where do you find electric charge or velocity in the article above?

Current = charge per unit time passing a given point. I = dQ/dt

[Bored chemist]

 ... the interaction between the light and photosensitive material is very much a  'photon and atoms' interaction much as described earlier.   At the point of interaction, the material was simply reacting to a deposit of energy by a photon ...

That energy is transferred when a force moves through a distance.
The force is applied to an electron and promotes it to a higher energy state.
The nature of the force is electrostatic in nature.
The electron reacts to that electromagnetic force.
Or do you think it's one of the other 3 fundamental forces that does it?

[hamdani yusuf]

Where do you find electric charge or velocity in the article above?

Current = charge per unit time passing a given point. I = dQ/dt

In my example, Q is constant over time.

[Eternal Student (OP)]

Hi.

That energy is transferred when a force moves through a distance.

   That's a result from mechanics, especially Newtonian mechanics.   Not all energy is transferred in a way that can be identified as some force moved through some physical distance.

   For the transfer of heat between two bodies, there doesn't need to be some force identified and some distance over which it was applied.   For example, a hot body does not push a colder body away, it just transfers heat.  (You can try to look microscopically and consider particles being agitated or accelerated by some force but if you look again with different glasses on then there are no particles, just waves.  Alternatively you just need to recognise something you ( @Bored chemist )  said in a different thread about temperature - temperature can be a measure of all sorts of internal energy in a substance and not just translational, rotational or vibrational motion of particles).

   The transfer of energy by waves is, of course, another example.   A water wave is a wave in something,  you could imagine that a superposition of two waves into a bigger wave (which is then a bigger lump of energy) happens because the water is being pushed up by some force from the other wave.  For an e-m wave, it does not have to be a wave in any material like "the aether".  Somehow the two waves just do combine and there is a big wave BUT there may not be any material or any force acting on that material that can be identified.   You obtain a bigger amount of energy in the final e-m wave but there was no material where mechanical forces had been applied over some physical distance.

   Getting directly to the situation being discussed:  For an atom and photon interaction,  the energy is transferred in some way that is not like some sort of mechanical force applied over some physical distance.   For example, you can't have two small forces that would sum up to the sufficient force (such as two low energy photons striking the electron).   You must have one photon of the right energy all in one go.   There is also no way you could use a smaller force but allow it to act over a larger physical distance   (I don't even know what that could mean or look like - the photon just interacts and there was no "distance" over which that force was applied).

Best Wishes.

[Bored chemist]

Hi.

That energy is transferred when a force moves through a distance.

   That's a result from mechanics, especially Newtonian mechanics.   Not all energy is transferred in a way that can be identified as some force moved through some physical distance.

   For the transfer of heat between two bodies, there doesn't need to be some force identified and some distance over which it was applied.   For example, a hot body does not push a colder body away, it just transfers heat.  (You can try to look microscopically and consider particles being agitated or accelerated by some force but if you look again with different glasses on then there are no particles, just waves.  Alternatively you just need to recognise something you ( @Bored chemist )  said in a different thread about temperature - temperature can be a measure of all sorts of internal energy in a substance and not just translational, rotational or vibrational motion of particles).

   The transfer of energy by waves is, of course, another example.   A water wave is a wave in something,  you could imagine that a superposition of two waves into a bigger wave (which is then a bigger lump of energy) happens because the water is being pushed up by some force from the other wave.  For an e-m wave, it does not have to be a wave in any material like "the aether".  Somehow the two waves just do combine and there is a big wave BUT there may not be any material or any force acting on that material that can be identified.   You obtain a bigger amount of energy in the final e-m wave but there was no material where mechanical forces had been applied over some physical distance.

   Getting directly to the situation being discussed:  For an atom and photon interaction,  the energy is transferred in some way that is not like some sort of mechanical force applied over some physical distance.   For example, you can't have two small forces that would sum up to the sufficient force (such as two low energy photons striking the electron).   You must have one photon of the right energy all in one go.   There is also no way you could use a smaller force but allow it to act over a larger physical distance   (I don't even know what that could mean or look like - the photon just interacts and there was no "distance" over which that force was applied).

Best Wishes.

The latent image in a photograph is composed of "out of place" electrons.
There's not many explanations for that which don't involve electromagnetic forces.

[alancalverd]

In my example, Q is constant over time.

and it is moving

[Petrochemicals]

Petro, there are no filters that can change the frequency of incident radiation. What I believe you are thinking about is certain crystals that perform frequency doubling operations such as infrared to visible, similar to the frequency doublers in common use in electronics. A lot of visible lasers generate at infrared and then double up to visible.

Petro, there are no filters that can change the frequency of incident radiation. What I believe you are thinking about is certain crystals that perform frequency doubling operations such as infrared to visible, similar to the frequency doublers in common use in electronics. A lot of visible lasers generate at infrared and then double up to visible.

Yep something like that, a crystal I think they used in the fusion lab recently. What is incident radiation.

[Eternal Student (OP)]

Hi.   Thanks for your comments @Bored chemist .   I don't especially agree but that's for only a minor reason.  Quite a lot of the interactions that seem to happen in photographic material are difficult to explain.  It is conventional to start using some reasonable Macroscopic or very mechanical models.  For example, the chemistry is almost always discussed with reference to atoms and electrons as if they are ordinary particles.  However, that's where I would target my concern.   

The latent image in a photograph is composed of "out of place" electrons.

   ?  I'm not sure what that was about.
   In a simple photographic material, like some silver halide held in a gelatin emulsion,  there is something called a "latent image centre" that forms when silver ions absorb an electron.   Those latent image centres are only stable when there's a few silver atoms all located close together,  the text I was just looking at suggested 3 or 4 silver atoms must be located close to each other to remain stable.  An earlier post from @alancalverd  suggested you needed two or more,  I'm not going to quibble over precisely how many you need, it's a small number.  Anyway, the latent image centre has a collection of whole silver atoms and not just some out of place electrons.   
    The free delocalised electrons were there, available for the silver ions to absorb, only because some photon had ejected an electron from the valence band of one halide particle and into the conduction band of the combined silver-halide lattice.  That happened somewhere in the structure.   Some of the Silver ions are free to move around through the crystal lattice and the electron is also quite free to move around.  So, usually the electron doesn't need to travel too far before it encounters some Silver ion that can absorb it, forming atomic silver.  Hence the latent image centre does usually form very close to where the original photon struck the photographic material (and that's why the photograph works, we have a latent image centre within nano-metres of where the photon struck the photographic material).   Anyway, the ejection of that electron to the conduction band was a quantum mechanical effect, it happened due to some interaction between a photon and an atom (well, a bromide ion rather than a whole atom).  That interaction is what I might have described as a 'photon-and-atom' interaction.

There's not many explanations for that which don't involve electromagnetic forces.

    There is no attempt to explain what mechanical forces applied when an atom modelled with Quantum Mechanics has an electron excited to another orbit by a photon.   Mechanical forces and solid particles on which they can be applied are not there or required to be there in a QM model of an atom.
    (There are, as you suggest, some explanations involving forces like an electrostatic force when the atom and its electrons are modelled just as some ordinary mechanical system).   

Best Wishes.

[evan_au]

change the frequency of incident radiation...certain crystals that perform frequency doubling operations such as infrared to visible

What is incident radiation?

This description refers to the familiar hand-held green laser pointer, which has an infra-red laser at 808nm, and a non-linear neodymium-doped frequency-doubling crystal which produces the emitted green beam at 404nm.
- The incoming, or "incident" radiation is infra-red from the pump laser
- The outgoing, or emitted radiation is green

https://en.wikipedia.org/wiki/Laser_pointer#Colors_and_wavelengths   (see subsection "Green")

a crystal I think they used in the fusion lab recently

This description refers to the US National Ignition Facility.

In this case, Xenon flash lamps are used to pump electrons in neodymium-doped glass into a high-energy state.

The incident radiation from the Xenon flash lamps is white light over a wide range of frequencies; only a tiny fraction of the light is at exactly the right frequency to produce the desired 1053nm laser pulse. This results in low efficiency for this type of laser, and is why NIF needs to cool down for 12 hours before attempting another pulse.
- This is unlike the hand-held laser pointer, where the incident infra-red energy is at just the right wavelength to produce the desired outgoing green beam, achieving quite high efficiency and allowing continuous operation (until the battery goes flat...).

https://en.wikipedia.org/wiki/National_Ignition_Facility#Laser

[Bored chemist]

the text I was just looking at suggested 3 or 4 silver atoms

And you get those atoms by pulling an electron off a halide ion and sticking it onto a silver ion.
Compared to the silver halide, those electrons are in the wrong places.