CDR: Re: Re: Choate physics again

[Michael Motyka]

Wasn't it grounding and Maxwell's equations last time? I can't believe
I'm falling for this again but here goes...

> On Thu, 28 Sep 2000, Michael Motyka wrote:
> 
> > >>By the time the coherent radiation (needed to make an image) passes
> > >
> > >Were not talking holograms, Jimmy-boy
>
> I didn't get the original message so I'll reply here.
>
Actually I didn't write this ^

I wrote this : 

I think what he was trying to convey were the effects of reflection,
absortion and diffusion.  etc...

> No, we're not talking about lasers. But then again 'coherent' simply means
> 'arranged' or 'synchronized'. If you don't believe there is coherence in
> imaging the rays of light through a camera then you don't have a fucking
> clue about optics.
>
I am not an optics expert but I DO have a clue. And any coherence in the
light that hits the film in my Canon as I snap one poorly composed photo
after another is purely accidental unless the scene has been painted by
a targetting system.

What is a laser Jim? LASER

Light
Amplification by the 
Stimulated
Emission of
Radiation

An atom in an excited state, ie one that is not in the ground state, may
be stimulated to release a photon by an incoming photon. The most
interesting part of this is that the emitted photon after the
interaction is in phase with the incoming photon and in the same
direction. Get lots of these interactions taking place in the right
medium and you get a river of photons all in phase. That's what coherent
means in optics - in phase.

Check your Webster's and please read the definition that says "3.
Physics. ..."

Go to any optics book. Want references?

Thermal radiation ( what you are imaging with your snooperscope ) is not
coherent by any definition that I know of. 

> The fact is, that if you take a lens and form an image there IS most
> certainly a level of coherence. You can break that coherence by simply
> injecting a fogged piece of glass for example.
> 
You could say that light and an optical system form a "coherent" image
because the image is recognizable but that usage might be confusing
because of the common and accepted use of coherent with reference to
LASER light. Form an image is probably adequately descriptive.

> This is what the walls of the house do, they break the coherence of the
> original light rays so that no image can be formed on the other side of
> the wall.
> 
The walls of the house do not "break the coherence." The more
interesting processes that would be going on at and in the walls of the
house would be reflection, scattering, absorption, diffusion( thermal)
and reradiation. These effects would probably vary widely with
construction materials and wavelength. The end result as these
wavelengths are incident on a wall might vary from little or no effect,
through blurring to outright shielding.

> Glass howerver is reasonably transparent and as a result the light doesn't
> lose coherence through that. However if you attenuate the light using an
> aluminized mylar sheet and then break up the image using the bubble pack
> (the little bubbles of air absord the IR and then re-emit it out of phase 
> with the original stream of photons - that! is coherence), walah. No
> usable image the cops can use against you.
> 
What your talking about is reflection, scattering, absorption etc...the
coherence of the light don't enter into it. 

> [Rest of a dumbass rant from another party deleted]
>
Go back to your physics boooks Jim. You missed it again on this one.
Damn I could kick myself for even trying. 

Mike