Groups > sci.physics.relativity > #403848

Re: Why is the speed of light slower in glass and regains its normal speeds as it exits from glass?

From	moroney@world.std.spaamtrap.com (Michael Moroney)
Newsgroups	sci.physics.relativity
Subject	Re: Why is the speed of light slower in glass and regains its normal speeds as it exits from glass?
Date	2017-01-03 05:14 +0000
Organization	The World : www.TheWorld.com : Since 1989
Message-ID	<o4fbv1$g4p$4@pcls7.std.com> (permalink)
References	(18 earlier) <slrno6hqin.hjp.nedlatham@woden.valhalla.oz> <o4bich$5ib$1@pcls7.std.com> <slrno6itj5.ql.nedlatham@woden.valhalla.oz> <o4c0iv$7t0$1@pcls7.std.com> <slrno6k73a.jah.nedlatham@woden.valhalla.oz>

Show all headers | View raw

Ned Latham <nedlatham@woden.valhalla.oz> writes:

>Michael Moroney wrote
>> Ned Latham writes:
>> >Michael Moroney wrote:

>> > > > > Single mode fiber (which doesn't work by the light bouncing off the
>> > > > > surface of the inner fiber, the light goes straight down the core)
>> > > >
>> > > > There is no evidence for that whatever.
>> > >
>> > > Yes there is, in what you snipped. 
>> >
>> > Bullshit. "Theory"-based assertions are not evidence.
>>
>> No, this is not "theory" but

>Learn to read. I said "theory"-based assertions.

Learn to snip properly.

>> No, this is not "theory" but well-established electromagnetic practice
>> including not only single mode fiber but microwave waveguide design.

Do you know anything about waveguides at all? How fiber is waveguides
for light?  What is the difference between TE00 and TE10 modes? What
mode(s) apply to multimode fiber? What mode(s) apply to single mode
fiber?  Will you answer any of this or just snip it?

>> > >: Single mode fiber (which doesn't work by the light bouncing off
>> > >: the surface of the inner fiber,

>That is speculation, pure and simple.
>There is no way it can have beem OBSERVED.

Sorry, it has been observed, and it is why single mode fiber was created
in the first place.  It is the job of engineers to take what scientists
have discovered and invented and create products from it, in this case,
single mode fiber which works over long distances.

Remember, the core of single mode fiber is only about 10 micrometers,
which is only about ~15 times the wavelength of the IR light used (after
correcting for the refractive index).  The ray theory of light doesn't
work in this case, it works only when the dimensions involved are quite
large compared to the wavelength.  The ray theory of light essentially
assumes a bunch of propagation modes exist, and these become total
internal reflection.  When the core is small enough, the number of
modes, which are quantized, get reduced, and you have to deal with the
wave equation.  Single mode fiber has the number of modes reduced to
one, which is straight down.  Remember, the reason for single mode in
the first place is because all those other modes propogate down the
fiber at different speeds and the usable data rate decreases with 
increased length.

>> Again, not "theory" or "speculation" but well-established electrical
>> engineering practice.

>Engineering practise is not process observation. You don't have
>to have the right idea about how a process proceeds in order to
>use it effevctively. Aeronautics is an infamous example of that.

You have to have the right idea to create single mode fiber in the
first place. Nobody would ever have created something like that which
must be quite difficult to make the very first time.  They made it because
theory said it would work, testing showed it did work (and matched theory)
and engineers made a useful product from it.

Engineers then modify the product because of different materials, 
different frequencies etc. using the theory and guess what? It works!
That means they really do have the right idea how it all works.

>> > Try to explain this: if the graduated refractive index
>> > of a single-mode fibre really does prevebt TIRs from occurring, why do
>> > manufacturers build those fivres with cladding layers?
>>
>> That's like asking why is there a need for the microwave "plumbing"  
>> itself in a microwave feed when the microwaves move through the air
>> inside.  It forms the waveguide.

>Wrong. Absent force at a distance, *nothing* can "guide" what it
>doesn't touch.

>You're not claiming force at a a distance, are you?

Ummm, electric charge? Magnetism? Gravity?

BTW with all your typos, I suspect you must be foaming at the mouth as you
reply. Perhaps you need to calm down first.

Thread

csiph-web