Roy Lewallen wrote:
Thanks, Jim for the correction. I had failed to notice that the graph
scale was normalized to wavelength. I stand corrected.

Roy Lewallen, W7EL

To be honest, I'm not sure which one is appropriate to integrate. In
theory, if you're integrating between two limits you'd use the
expression that matches how the limits are specified..

That is, if you wanted to get the energy between 350 and 600 nm, then
you'd use the energy/nm

OTOH, if you wanted to integrate between 470 THz and 800THz, you'd use
energy/Hz.

they "should" come out with the same answer (especially in the limit of
actual integration with respect to d(nu) or d(lambda)).

It's probably only when you do a rough and ready numerical integration
(or do it by eye off the graph) that it makes a difference.

Actually, it's kind of interesting that you brought it up, because, like
you, I'd always seen the W/nm with a linear scale in nm graphs...

On Tue, 04 May 2010 12:08:28 -0700, Jim Lux
wrote:

That is, if you wanted to get the energy between 350 and 600 nm, then
you'd use the energy/nm

OTOH, if you wanted to integrate between 470 THz and 800THz, you'd use
energy/Hz.

The units would cancel unless that is your intent - but I am still
stymied by what is being sought by these elaborations.


they "should" come out with the same answer (especially in the limit of
actual integration with respect to d(nu) or d(lambda)).

Hence my question about the significance of changing domains when
either integration must, ultimately, come to the same thing in power.
None of this is currently being expressed in energy (a term being
commingled with power), which for optoelectronics would be eV.

This would raise a curious representation of a third domain with
re-rigging the wavelength/frequency scale into the appropriate energy
scale of eV vs. power. The solar radiation spectrum would thus span
(left to right) 5eV to 0.5eV.

Where is this leading?

73's
Richard Clark, KB7QHC

On Apr 30, 2:14*am, "Peter" wrote:
I'm preparing an article for a local radio club magazine about the nature of
radio and electromagnetic radiation in general. While this is a non
mathematical and general descriptive treatment of the subject it is a
challenge to make it clear and consistent.
I know this group has some expertise on this subject and would appreciate
any constructive comment and suggestions regarding the attached article.

http://members.optushome.com.au/vk6ysf/vk6ysf/radio.htm

Thank you for your time.

Regards Peter VK6YSF

For what it's worth...

I've often found it useful to consider alternate ways to think about
things. In this thread, there have been some comments about electric
fields, magnetic fields and electromagnetic fields. So, I ask: how
do we measure fields? As far as I know, it's by their interaction
with matter: we observe how an electromagnetic field accelerates
electrons, for example. Do we have any way other than by observing
how a (E, M, or EM) field interacts with matter to measure a field?
If not, does a field _necessarily_ have any physical reality, any
reality beyond a mathematical model to explain what we observe?

I suppose some here won't be ready to contemplate this in any depth,
though others may find it enlightening.

One might say that radio is the practical use of the observed physical
effect that accelerating charges in one place leads to free charges at
distant points being accelerated, in a manner we're able to describe
pretty accurately, so far as we know now, with our models.

Cheers,
Tom

On Tue, 4 May 2010 18:16:26 -0700 (PDT), K7ITM wrote:

For what it's worth... Do we have any way other than by observing
how a (E, M, or EM) field interacts with matter to measure a field?

Hi Tom,

You ask if we have "any way other... [than where a field] interacts
with matter." In a side thread, there is the discussion of heat. Heat
is a quasi-particle which means it does not exist as a physical
entity, but it acts like one (shades of photon duality). Heat is
wholly without matter, but in the whole absence of matter there is no
such thing as heat.

As to the remainder of the quote "to measure." This demands
physicality and your statement is self-negating in its plea.

If we rewind to the beginning of the plea, "observing" is a physical
interference described by Heisenberg. The bookends of your plea are,
then, doubly negating. That or (and here the thread returns to
metaphysics once again) interactions go unwitnessed - which is an
existential negation.

Expecting any reports from the Cat in the Box? Perhaps through an
entangled cat?

73's
Richard Clark, KB7QHC

K7ITM wrote:

For what it's worth...

I've often found it useful to consider alternate ways to think about
things. In this thread, there have been some comments about electric
fields, magnetic fields and electromagnetic fields. So, I ask: how
do we measure fields? As far as I know, it's by their interaction
with matter: we observe how an electromagnetic field accelerates
electrons, for example. Do we have any way other than by observing
how a (E, M, or EM) field interacts with matter to measure a field?
If not, does a field _necessarily_ have any physical reality, any
reality beyond a mathematical model to explain what we observe?

. . .

On the first day of the first class of Electromagnetic Fields, I asked
the professor (Carl T.A. Johnk, author of _Engineering Electromagnetic
Fields and Waves_), "What is an electromagnetic field?" His answer:
"It's a mathematical model we use to help us understand phenomena we can
observe and measure." And I see that in the second paragraph of his book
he writes "A field is taken to mean a mathematical function of space and
time." I've been satisfied with that definition.

Roy Lewallen, W7EL

4 "Roy Lewallen" wrote
...
K7ITM wrote:

For what it's worth...

I've often found it useful to consider alternate ways to think about
things. In this thread, there have been some comments about electric
fields, magnetic fields and electromagnetic fields. So, I ask: how
do we measure fields? As far as I know, it's by their interaction
with matter: we observe how an electromagnetic field accelerates
electrons, for example. Do we have any way other than by observing
how a (E, M, or EM) field interacts with matter to measure a field?
If not, does a field _necessarily_ have any physical reality, any
reality beyond a mathematical model to explain what we observe?
. . .

On the first day of the first class of Electromagnetic Fields, I asked the
professor (Carl T.A. Johnk, author of _Engineering Electromagnetic Fields
and Waves_), "What is an electromagnetic field?" His answer: "It's a
mathematical model we use to help us understand phenomena we can observe
and measure." And I see that in the second paragraph of his book he writes
"A field is taken to mean a mathematical function of space and time." I've
been satisfied with that definition.

Wiki wrote: "The field can be viewed as the combination of an electric field
and a magnetic field. The electric field is produced by stationary charges,
and the magnetic field by moving charges (currents); "

But what produce very slow charge?

Next Wiki weote: "From a classical perspective, the electromagnetic field
can be regarded as a smooth, continuous field, propagated in a wavelike
manner ;"

It is important to know that Maxwell's waves are rotational (oscillating
magnetic whirl).

Alternate electric field also propagate in a wavelike manner. But here to
and fro (no rotations).

The fundamental question: Are radio waves a simple electric waves or the
very sophisticated Maxwell's waves?
S*

On May 3, 7:25*am, "Szczepan Bialek" wrote:
*Radio waves from the dipole are polarized. Does it mean that light is
emitted by a dipoles?

sure, why not? but polarized waves can be emitted from other things
also.


We can shield the one end of the dipole.

no you can't.


Why the dipoles exhibit the directional pattern?

because they do, its well measured and accurately described in the
equations.

On May 5, 8:52*am, "Szczepan Bialek" wrote:

Wiki wrote: "The field can be viewed as the combination of an electric field
and a magnetic field. The electric field is produced by stationary charges,
and the magnetic field by moving charges (currents); "

an electric field can also be created by a changing magnetic field...
and a magnetic field by a changing electric field... no charges
needed.


But what produce very slow charge?

a charge is a charge, it can neither be created nor destroyed.... well
except maybe by matter-anti-matter annihilation. charged particles
can move at any speed from 0 to c, nothing special about speeds.


Next Wiki weote: "From a classical perspective, the electromagnetic field
can be regarded as a smooth, continuous field, propagated in a wavelike
manner ;"

It is important to know that Maxwell's waves are rotational (oscillating
magnetic whirl).

no they aren't... at least not all of them. maxwells equations are
just as well satisfied by linearly polarized (magnetic AND electric
field) waves.


Alternate electric field also propagate in a wavelike manner. But here to
and fro (no rotations).

if the magnetic field is rotating then the electric field also
rotates. they always go together.


The fundamental question: Are radio waves a simple electric waves or the
very sophisticated Maxwell's waves?

ALL radio waves can be described by maxwell's equations, both simple
linear polarized ones and circularly polarized ones.

The fundamental question: Are radio waves a simple electric waves or the
very sophisticated Maxwell's waves?

ALL radio waves can be described by maxwell's equations, both simple
linear polarized ones and circularly polarized ones.

The fundamental question is really how can we describe this "wave".? A
wave of what "water",
A wave of "water" traveling towards a beach.
Is it water we are really trying to describe or what?
Water has a "skin" on its surface , a skin that encasulates it like a
bag , container or a boundary!
Nothing is clear when describing a "wave" with respect to physics, as
it is just a "F" word to substitute an unexplainable in a psuedo
description
There is no agreement what so ever as to what a "wave" is so there
cannot exist a description of what radio "IS", "IS"!. Physicists
acknowledge that radio is some thing that is unexplanable leaving just
hams to fill in the unexplainable about radio and to deny the
explanations made by others.
What we do have is a string of mathematical equations all of which
interlock which are a result
of observation and seamingly reasonable deductions. Maxwell deduced b
y examination of units used that a portion of his formula was also a
mathematical explanation of elevation and acceleration but no
description of what! A physicists
named Gauss who provided a lot of Maxwells tools
used Newtons laws to establish boundary laws where it can be seen that
mathematically a clump of static particles in equilibrium could be
made
dynamic by adding a time varying field while retaining equilibrium
meshes with Maxwells equations on radiation. So who on earth descided
to interject "waves" into the discussion and why?
And what experiment was performed that dictated its inclusion in the
subject of radio or radiation that has put a screaming halt to a
sustainable explanation of same for more than a hundred years
where other dreams have come to fruition by utelizing the human brain.
Is it the ham population
that is responsible for the lack of advances in the advancement of
science by denying the inclusion of particles as the basic matter
involved in elevation and acceleration (displacement) as implied by
Maxwell's equations, preferring instead to use 'water' and 'waves' to
describe the science to the non initiated.

"K1TTT" wrote
...
On May 3, 7:25 am, "Szczepan Bialek" wrote:
Radio waves from the dipole are polarized. Does it mean that light is
emitted by a dipoles?

sure, why not? but polarized waves can be emitted from other things
also.


We can shield the one end of the dipole.

no you can't.

A whip antennas on a car is not such?

Why the dipoles exhibit the directional pattern?

because they do, its well measured and accurately described in the
equations.

Are the measured and the calculated from the equations in agreement?

S*