Radio waves vs light waves

[Jay Honeck]

Okay, here's a weird one for the group: Radio waves are the same as light
waves, except they're not in the visible spectrum, right?

Here's why it matters: As we were departing from Muscatine, IA today (a
beautiful day to fly in the Midwest, BTW -- clear and warm) after a great
lunch, my gaze fell on their on-field VOR transmitter. Focusing closely on
the "Hershey's Kiss"-shaped structure (with my new glasses -- wow, what a
difference a new prescription makes!), I wondered aloud if the lens in my
eye was at that moment focusing powerful radio waves onto my retina.

Mary, a scientist with a strong physics background, was not sure if radio
waves behaved the same as light waves.

I've never heard of anyone frying their retinas by looking at a radio
transmitter, but this begs the question: Can the lens in your eye focus
radio waves?

If not, why not?
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Steve Foley]

Jay,

a) If you've seen a prism (or the cover of Dark Side of the Moon), you see
that different colors are affected differently when they pass through glass.
The differences if these colors are the wavelength. I suspect eyeglasses are
designed to focus 'average' colored light. I also suspect they will not
focus radio waves.

b) The rods and cones in your eyes are not sensitive to radio waves. (Unless
there's something you're not telling us)


"Jay Honeck" > wrote in message
news:%uRYb.353608$na.522124@attbi_s04...
> Okay, here's a weird one for the group: Radio waves are the same as light
> waves, except they're not in the visible spectrum, right?
>
> Here's why it matters: As we were departing from Muscatine, IA today (a
> beautiful day to fly in the Midwest, BTW -- clear and warm) after a great
> lunch, my gaze fell on their on-field VOR transmitter. Focusing closely
on
> the "Hershey's Kiss"-shaped structure (with my new glasses -- wow, what a
> difference a new prescription makes!), I wondered aloud if the lens in my
> eye was at that moment focusing powerful radio waves onto my retina.
>
> Mary, a scientist with a strong physics background, was not sure if radio
> waves behaved the same as light waves.
>
> I've never heard of anyone frying their retinas by looking at a radio
> transmitter, but this begs the question: Can the lens in your eye focus
> radio waves?
>
> If not, why not?
> --
> Jay Honeck
> Iowa City, IA
> Pathfinder N56993
> www.AlexisParkInn.com
> "Your Aviation Destination"
>
>

[Jim]

Be sure to bring a bottle of that to OSH this summer Jay! :)
Just kidding.
Ok, here's another weird one... if light is supposed to be made up of both
waves and particles, how much does it weigh? How much resistance do light
particles have on an airplane in flight? Do you have longer range at night?
Does a light bulb weigh more when it's on or when it's off?
--
Jim Burns III

Remove "nospam" to reply

[Katherine]

> Ok, here's another weird one... if light is supposed to be made up of both
> waves and particles, how much does it weigh?

E = mc^2. So a photon (light particle) has an relativistic mass equal
to its energy divided by the speed of light squared. For visible light,
a photon's energy is a few electron-volts (eV)

How much resistance do light
> particles have on an airplane in flight?

It has some, yes. Physicists call it "radiation pressure" and it's
measureable in a lab. But in the air it's not much compared to the
pressure due to your average Nitrogen atom which is much more massive
(1,300,000,000 eV of energy).

Do you have longer range at night?
> Does a light bulb weigh more when it's on or when it's off?

In a manner of speaking, yes. There's more energy present when the
light bulb's on (in both light and heat), and since energy equals mass
(ala Einstein, above), it does "weigh" more. The extra mass/energy
comes from the wall socket.

To noticably refract radio waves, I think you'd need something with a
thickness at least on the order of the wavelength of the waves. VHF
radio has wavelengths on the order of several meters.

Hope i did all that math right,

--Kath

[Peter Duniho]

"Jay Honeck" > wrote in message
news:%uRYb.353608$na.522124@attbi_s04...
> [...]
> I've never heard of anyone frying their retinas by looking at a radio
> transmitter, but this begs the question: Can the lens in your eye focus
> radio waves?

No. Even though they are "the same" kind of physical manifestation, the
difference in wavelength is very significant. Radio waves behave "the same"
as light waves in that they can be blocked, reflected, refracted, etc. but
because of the frequency difference, it will require different kinds of
materials to produce "the same" effects.

The lens in your eye is not going to have any significant effect on the
transmission of radio waves through that lens.

Which is not to say that "powerful radio waves" are not landing on your
retina. They are. They just haven't been focused by your eye's lens.

There's nothing to worry about though. We are all constantly bombarded by
radio waves coming from every direction, in all sorts of wavelengths.
"They" say that the radio waves are harmless. You believe "them", don't
you? :)

Pete

[Teacherjh]

>> Can the lens in your eye focus radio waves?

No.

There are many reasons for this, the most fundamental is that EM radiation (the
general term for "light of any wavelength even if it's not 'visible' light")
(EM stands for electromagnetic) reacts differently to matter depending on the
frequency ("color"). Some colors are absorbed, some are reflected, some are
transmitted. This is what makes something green, or blue, or white. In fact,
white flowers often reflect differeing amounts of UV radiation, so bees can see
a difference. This remains true throughout the entire EM spectrum. Water
absorbs IR radiation but passes visible light. Glass absorbs UV and IR,
passing visible light. If you go to your dentist and get an X-ray, the device
they focus on you passes X-rays but does not pass visible light. And so on.

As for focusing, this involves refraction, which has to do with the difference
between the speed of light in a vacuum, and the speed of light in the substance
it is passing through. (think of the matter as interfering with the light
waves as they go by, slowing them down to some extent). The amount of
refraction (if any) has to do with the frequency of the light to begin with.
"Chromatic abberation" is a defect in lenses caused by the fact that different
colors are refracted different amounts (and is the reason prisms work in the
first place). So, a lens that is designed for one wavelength will not work as
well with other wavelengths.

In the case of visible light, the wavelengths are within a factor of two of
each other. (purple, the shortest, is only half as big as red, the longest).
Radio waves are MUCH longer wavelength. Some of them can be the size of a
football field, while others are only a few inches long. That's a pretty wide
variation, and is very different from the wavelength of light (which is very
VERY tiny - much smaller than a microbe). In fact, the waves sent out by the
VOR are bigger than your eye itself. Not much chance of focusing there!

Incidentally, the wavelength is inversely proportional to the frequency. The
speed of light is about 300,000,000 meters per second. So, if you have a
wavelength of 100 mHz (close to VOR frequency), that means that 100,000,000
waves are going by every second. So, one second's worth of those waves
(traveling at the speed of light) are spread out over 300,000,000 meters.
Divide the two... 300,000,000 / 100,000,000 gives you 3 meters, or almost ten
feet. ONE wave is ten feet long! Your eye isn't focusing that worth squat!

>>
if light is supposed to be made up of both waves and particles...
<<

It's not. It is neither a wave nor a particle... in fact the concept of wave
and particle don't really apply to things of this nature. However, light
BEHAVES as if it were a particle sometimes, and behaves like it were a wave
other times. It never does both at once, and which it does depends on what you
are trying to observe. (yes, it depends on what you look at! weird!)

>>...how much does it weigh?

It weighs nothing but it has energy. Energy and mass are the same, like water
and ice are the same. When you turn on a flashlight, the flashlight does get
lighter, and all that mass is turned into energy sent out as light. The
difference is not very much, but it is there. The atom bomb works this way
too... only by harnessing nuclear rather than chemical reactions, the amount of
energy released is considerably greater.

Light does have momentum. If you shine a light on something, there is a
recoil, and it does push the illuminated object away. It just doesn't do it
very strongly. Solar sails work on this principle (to my knowledge they have
not yet been demonstrated, but they are a serious contender for unmanned
interplanetary flight). Again, it's a VERY weak force, but it is there, and
even a weak force, applied for long enough, out in space where there isn't much
resistance, can get you moving quite fast eventually.

That should get you started thinking.

Jose




--
(for Email, make the obvious changes in my address)

[Jay Honeck]

> That should get you started thinking.

A master of understatement you are, in addition to being an excellent
teacher.

Thanks!
--
Jay Honeck
Iowa City, IA
Pathfinder N56993
www.AlexisParkInn.com
"Your Aviation Destination"

[Jim]

Holy crap, I knew somebody would know, but now I've got a splitting
headache. I wonder what happens to all the particles of light that can't
make it through windows. Do they pile up on the window sill? Never mind,
my brain hurts :)

Jim

[C J Campbell]

"Katherine" > wrote in message
...
> > Ok, here's another weird one... if light is supposed to be made up of
both
> > waves and particles, how much does it weigh?
>
> E = mc^2. So a photon (light particle) has an relativistic mass equal
> to its energy divided by the speed of light squared. For visible light,
> a photon's energy is a few electron-volts (eV)
>
> How much resistance do light
> > particles have on an airplane in flight?
>
> It has some, yes. Physicists call it "radiation pressure" and it's
> measureable in a lab. But in the air it's not much compared to the
> pressure due to your average Nitrogen atom which is much more massive
> (1,300,000,000 eV of energy).
>

Still, there has been some research into the idea of using light as means of
propulsion, either in something like solar sails or by using lasers to
bombard objects enough to cause them to move.

[C J Campbell]

"Jim" > wrote in message
...
> Holy crap, I knew somebody would know, but now I've got a splitting
> headache. I wonder what happens to all the particles of light that can't
> make it through windows. Do they pile up on the window sill? Never mind,
> my brain hurts :)
>

Particles of light that do not make it through the window and which are not
reflected by the surface are absorbed into the structure. The excess energy
is then radiated away as heat.

The difference between a particle and a wave is the difference between
ripples on the water and the stone you threw in there. The particle is the
object itself. Waves are the measurable effect of the passage of the
particle. It is a fundamental axiom of physics that for very small particles
you can measure either the wave or the particle, but not both
simultaneously. Hence you can look at light as either a wave and measure its
characteristics in that manner, or you can look at where a particular photon
is and measure its characteristics at that moment. The reason is there is
nothing small enough to see both. How would you 'see' a photon, no matter
how much you magnified it? All you can see is where it went.

The light bulb does not create photons. It emits photons that are already
stored in the bulb. It probably absorbs enough electrons in the process so
that its weight does not change significantly.

[Ross Oliver]

Everyone else has focused (!) on wavelength, but no one has mentioned
radiated power. Wavelength is to color as power is to brightness.
Anyone know how many watts a VOR transmitter radiates?
I would suspect is it no more than a few hundred, about equivalent to
a common outdoor floodlight. The energy of even the reflected sunlight
reaching your eye, Jay, was probably several orders of magnitude
more than the energy from the VOR.


Ross Oliver

[Jim Fisher]

"Jim" > wrote in message
> Ok, here's another weird one... if light is supposed to be made up of both
> waves and particles, how much does it weigh?

It is my understanding that light is not "made" of waves or particles but
waves or particles can be used to describe their behavior depending on how
one wishes to observe them ("wave/particle duality", I think it's called).

Then again, if you observe the wave/particle, your observation changes the
outcome of the observation. This is called the "Ya Just Nevah Know" theory.

Weird stuff, that physics.

But here's another one that I got from a book a friend form here mailed to
me some time ago: You are inside a perfect sphere that has a mirror
surface. Your eyes are squarely (or is it"sperely") in the middle of the
sphere. What does the reflection look like?

--
Jim Fisher

[Teacherjh]

>>
But here's another one that I got from a book a friend form here mailed to
me some time ago: You are inside a perfect sphere that has a mirror
surface. Your eyes are squarely (or is it"sperely") in the middle of the
sphere. What does the reflection look like?
<<

It looks like the sound of one hand clapping.

Mu

Jose

--
(for Email, make the obvious changes in my address)

[Teacherjh]

>>
Particles of light that do not make it through the window and which are not
reflected by the surface are absorbed into the structure. The excess energy
is then radiated away as heat.
<<

Sort of.

They are absorbed, which means the (electromagnetic) energy is converted into
other kinds of energy in the structure, be it raising the orbitals of
electrons, wiggling the atoms around a bit, or accelerating it. The excess
energy is not really "excess" as there is no amount of energy a structure is
"permitted" to have. (not counting enough energy to blow it up. :) Molecular
motion IS heat. One of the ways energy is dissipated is the ratdiation of
photons (light, be it infra-red or otherwise), another is physical transfer of
momentum (the structure's atoms bounce against air molecules and make the air
molecules go faster). There are more.

>>
The difference between a particle and a wave is the difference between
ripples on the water and the stone you threw in there.
<<

No, the stone and the water are different things. But light, whether thought
of as waves or as particles, is the same thing. And if you think of light as a
particle, you are wrong. If you think of it as a wave, you are also wrong.
That's just the way the universe was put together - it's not my fault. <g>.

>>
It is a fundamental axiom of physics that for very small particles
you can measure either the wave or the particle, but not both
simultaneously.
<<

True enough.

>>
The reason is there is nothing small enough to see both.
<<

Never thought of it that way, but I don't think it's quite right. I thnk the
reason is more fundamental. "Stuff" is just made of something we don't
understand, and the ways we have though of so far are inadequate when put to
the test, though they make perfect sense in the macroscopic sense.

>>
The light bulb does not create photons. It emits photons that are already
stored in the bulb.
<<

The bulb too does create photons... photons that didn't exist before. It does
so by resisting the motion of electons, and therefore sucking some of their
energy into making the bulb hot, and this releases energy in the form of
photons.

Ok, so just what IS a photon?

Think of an electric field that points up and down, and keeps on switching
directions at some rate. Now think of a magnetic field that points left and
right, but switches directions at the same rate, just a bit out of phase. As
the electric field collapses it generates a magnetic field, and as the magnetic
field collapses it generates an electric field, and the two chase each other at
the speed of light. It's not a perfect description, but it's pretty close to
what a photon is.

It takes energy to make these fields wiggle like that, the energy comes from
the motion of electons in their orbitals. When things happen just right, the
electron collapses, exhausted, back into a lower orbital, and a spurt of energy
in the form of the wiggling Electric and Magnetic fields shoots out. A photon
has been emitted. That's where they come from.

Jose


--
(for Email, make the obvious changes in my address)

[Buff5200]

Jay Honeck wrote:

>Okay, here's a weird one for the group: Radio waves are the same as light
>waves, except they're not in the visible spectrum, right?
>
>I've never heard of anyone frying their retinas by looking at a radio
>transmitter, but this begs the question: Can the lens in your eye focus
>radio waves?
>
>If not, why not?
>

Ok, I'll try to keep it simple and free from techno babble:

1. I'm an electronics engineer for CBS television network, trust me.

2. Radio waves, micro waves, visible light, x-rays are all
"electromagnetic (EM) radiation". BUT...
as the frequency changes, the physical properties change. Thats one
reason they have
different names.

3. The lenses of your eyes DO NOT focus radio waves, micro waves, or
x-rays. Only
visible light and adjacent EM radiation like infra-red and
ultra-violet.

4. Low level radiation does not harm your eyes. But if you get close
enough to a live, high power
radio transmitter, the radio waves CAN cause damage. Like the flame
from an arc-welder.
If you look at an arc-welding flame from 1,000 ft away, no
problem. If you look at
an arc welding flame from 2 feet away (no protection) you get
fitted for a white cane.
Just stay a few feet away from any HIGH POWER radio transmitter and
there is
no health problem. Low level transmitters like cell phones do not
cause medical problems,
only internet rumors.

5. Consider the following examples of how different forms of EM
radiation have different
physical properties:

-Soda Glass will totally block ultra-violet light while passing
radio waves, microwaves,
visible light, and x-rays.

-A sheet of black paper will block visible light, but pass radio
waves, microwaves, and
x-rays.

-A glass of water will partially block radio waves, totally block
microwaves, partially block
light waves, and pass x-rays.

-A sheet of aluminum foil will totally block radio waves,
microwaves, light waves, but
pass x-rays. (nothing but a couple tons of lead totally blocks
x-rays)

>
>

[Jim Fisher]

"Teacherjh" > wrote in message
When things happen just right, the
> electron collapses, exhausted, back into a lower orbital, and a spurt of
energy
> in the form of the wiggling Electric and Magnetic fields shoots out. A
photon
> has been emitted. That's where they come from.

Pretty cool description, Teach. Heck, my Alabama brain can almost grasp
that concept.

Unfortunately, when it comes to physics the more I think I grasp, the less I
actually grasp. This is called the Aintcertainty Principal.

--
Jim Fisher

[Craig Prouse]

In article >,
"Jim Fisher" > wrote:

> Then again, if you observe the wave/particle, your observation changes the
> outcome of the observation. This is called the "Ya Just Nevah Know" theory.

Also known as the Heisenberg Uncertainty Principle.

Computer bugs that only happen when you disable your debugging tools are
therefore known as "Heisenbugs."


Scrawled on a toilet stall at Caltech sometime in the early '80s:

"Heisenberg sat here yesterday."

Then, in different handwriting immediately below:

"Pauli was here at the same time."


I'll explain it anyone wants, but Teacherjh seems to be doing a better
job with explaining this stuff that I probably could.

[Jim Weir]

You kept it out of technobabble, but you kept it far from the truth.

Would you mind not stepping into an argument where you have not a clue as to the
answer?

Jim

Buff5200 >
shared these priceless pearls of wisdom:

->>
->
->Ok, I'll try to keep it simple and free from techno babble:


Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Peter Duniho]

"Ross Oliver" > wrote in message
...
>
> Everyone else has focused (!) on wavelength, but no one has mentioned
> radiated power.

That's because the question was "does my lens focus the radio waves", not
"is my retina being cooked".

Duh.

[Tim Witt]

Jim Weir > wrote in message >...
> You kept it out of technobabble, but you kept it far from the truth.

So how about explaining what was untruthful, rather than offering a
drive-by shooting critique. I read these posts to get smarter not as
a forum for putdowns.

[Thomas Borchert]

Katherine,

> Physicists call it "radiation pressure" and it's
> measureable in a lab.
>

you can drive spaceships with it, though. There's a great scifi story
by Arthur C. Clarke about a solar yacht race using radiation pressure
from the sun on big "sails".

--
Thomas Borchert (EDDH)

[Teacherjh]

>>
Scrawled on a toilet stall at Caltech sometime in the early '80s:
"Heisenberg sat here yesterday."
Then, in different handwriting immediately below:
"Pauli was here at the same time."
<<

I was there. It goes:

"Heisenberg might have been here."
"Pauli was here too, but not at the same time."

It refers to the Heisenberg uncertanty principle (one can measure the position
or momentum of a particle, but not both at the same time (*)), and the Pauli
exclusion principle (no two electrons (**) can be in the same state at the same
time)

(*) You can measure them both, but the more accurately you measure one, the
less accurate the other is. It's not too farfetched to say that the concept of
a particle having a precise position and momentum at the same time is
meaningless.

(**) Not just electrons, but an entire class of particles (called Fermions)
behave this way. Common fermions are electrons, protons, and neutrons.
Compare with Bosons, which like to be in the same state. Photons are bosons,
which is why a laser works... all the light waves can line up in step. An
electron laser would be impossible (or would lead to a huge physics advance)

All this is related to aviation in that thinking about it makes one high. <g>

Jose


--
(for Email, make the obvious changes in my address)

[Nathan Young]

On Thu, 19 Feb 2004 13:17:36 +0100, Thomas Borchert
> wrote:

>Katherine,
>
>> Physicists call it "radiation pressure" and it's
>> measureable in a lab.
>>
>
>you can drive spaceships with it, though. There's a great scifi story
>by Arthur C. Clarke about a solar yacht race using radiation pressure
>from the sun on big "sails".

I've always wondered about the following:

Ok - so we all agree that a light puts out a small amount of force.
Newton tells us that an equal an opposite amount of force would be
directed in the opposite direction. F=ma.

So why can't we use high-intensity lights powered by a nuclear reactor
as a source of space propulsion? Is the F so small and the 'm' so
large that the 'a' would be miniscule? There's no wind resistance to
overcome in space, so you don't have to fight against that. I imagine
gravity would still be a factor though.

-Nathan

[John Gaquin]

"Jay Honeck" > wrote in message news:%

> ....Radio waves are the same as light
> waves, except they're not in the visible spectrum, right?
>
> .....I wondered aloud if the lens in my
> eye was at that moment focusing powerful radio waves onto my retina.

[fade theme].......You're traveling through another dimension....a dimension not only of sight and sound but of mind....

[John Gaquin]

"C J Campbell" > wrote in message >
> Particles of light that do not make it through the window and which are
not
> reflected by the surface are absorbed into the structure.

So, over the course of time your house gets lighter?

[John Gaquin]

"Teacherjh" > wrote in message

> ....Compare with Bosons, which like to be in the same state.

Not true. There used to be great herds of bosons, and they would roam
across several states in the great plains. They're gone now.

:-)

[Andrew Sarangan]

Jay

The wavelength of a VOR transmission is about 8ft long. The wavelength
of a visbile light is about 0.5 micrometer. You can fit thousands of
wavelengths inside the pupil of your eye, but you cannot fit even a
small fraction of a radio wave. For a lens to behave like a lens, its
size must be much larger than a wavelength. If it is smaller, only a
tiny fraction of a wavelength will get through. It's like trying to
squeeze a large object through a small hole. Insteading of focusing,
it simply scatters (diffracts).

If you are concerned about a VOR, consider that commercial radio and
TV stations transmit at much higher power levels. Think about that
next time you stare at a TV tower :-)




"Jay Honeck" > wrote in message news:<%uRYb.353608$na.522124@attbi_s04>...
> Okay, here's a weird one for the group: Radio waves are the same as light
> waves, except they're not in the visible spectrum, right?
>
> Here's why it matters: As we were departing from Muscatine, IA today (a
> beautiful day to fly in the Midwest, BTW -- clear and warm) after a great
> lunch, my gaze fell on their on-field VOR transmitter. Focusing closely on
> the "Hershey's Kiss"-shaped structure (with my new glasses -- wow, what a
> difference a new prescription makes!), I wondered aloud if the lens in my
> eye was at that moment focusing powerful radio waves onto my retina.
>
> Mary, a scientist with a strong physics background, was not sure if radio
> waves behaved the same as light waves.
>
> I've never heard of anyone frying their retinas by looking at a radio
> transmitter, but this begs the question: Can the lens in your eye focus
> radio waves?
>
> If not, why not?

[Dennis O'Connor]

Ya did really good...
Just one point... to effectively refract <i.e., focus> radio waves the
antenna can be as small as one half wavelength in dimension...
If I had a chalk board on here where I could scribble and wave my hands it
would become clear - taint clear unless I talk with my hands - It's the
time/phase delay due to C that allows a half wavelength structure to
effectively refract,
<i.e. the arrows all add up to the shortest path - see R. Feinman, et. al.>

Larger is better, however... Look at the dish at Arecibo for example..
http://www.rainforestsafari.com/observe.html
It is an efficient focuser of very weak, short wave length, radio waves
because it is many wavelengths across, gathering numerous wave fronts in
phase, and focusing them on the sampling probe...

Similarily, a camera lens that works efficiently at lower light levels will
be larger in diameter for a given focal length than one that doesn't work as
efficiently... i.e., an f:2.8 lens versus an f:1.4 lens..

denny
"Katherine" > wrote >
> To noticably refract radio waves, I think you'd need something with a
> thickness at least on the order of the wavelength of the waves. VHF
> radio has wavelengths on the order of several meters.
>
> Hope i did all that math right,
>
> --Kath

[Dennis O'Connor]

No, the cornea is too small in terms of wavelength to effectively refract,
<focus> radio waves... Plus there is the issue of the low refractive index
of the lens at radio frequencies, even were it were large enough...

That's not to say that radio waves cannot cause heating damage to the
tissues of the cornea and the retina, even if unfocused, as they pass
through your body...
The millimeter wavelengths - including your microwave oven - can certainly
heat damage body tissues, ask any hotdog...
But a discussion of that has to include the wavelengths involved, the
intensity of the radio field at that point in space, the temporal length of
exposure, etc... Too big a topic for this type of forum, but radar
technicians have accidently had eye damage from looking into a working
antenna...

Interestingly, <or maybe not> ham radio operators have to fill out an
engineering form that quantifies the level of exposure to radiation of
people near to their antennas and file it with the government... If you
have more than a passing interest in that item let me know and I'll refer
you to the relevant literature...

cheers ... denny

"Jay Honeck" > wrote I wondered aloud if the lens
in my
> eye was at that moment focusing powerful radio waves onto my retina.
>

[Teacherjh]

>>
There used to be great herds of bosons, and they would roam
across several states in the great plains. They're gone now.
<<

Nope. They are in Washington DC. All in the same state. The state of
confusion.

Jose

--
(for Email, make the obvious changes in my address)

[Teacherjh]

>>
So why can't we use high-intensity lights powered by a nuclear reactor
as a source of space propulsion?
<<

They can. But the F is small, so you need a lot of t to reach much of a v, as
long as you are far enough from a g.

Such systems have only been developed in science fiction however because we are
not yet doing enough interstellar travel, and people are uncomfortable with
nuclear reactors in space.

Jose

--
(for Email, make the obvious changes in my address)

[Teacherjh]

>>
radar technicians have accidently had eye damage from looking into a working
antenna...
<<

or even looking away from... as proximity is the only important factor, not
orientation.

Jose


--
(for Email, make the obvious changes in my address)

[Thomas Borchert]

John,

> > ....Compare with Bosons, which like to be in the same state.
>
> Not true. There used to be great herds of bosons, and they would roam
> across several states in the great plains. They're gone now.
>

But now, the Bozos roam there.

--
Thomas Borchert (EDDH)

[One's Too Many]

"Peter Duniho" > wrote in message >...
> "Ross Oliver" > wrote in message
> ...
> >
> > Everyone else has focused (!) on wavelength, but no one has mentioned
> > radiated power.
>
> That's because the question was "does my lens focus the radio waves", not
> "is my retina being cooked".

There have been cases of people getting their eyeballs and other body
parts "cooked" by exposure to strong RF, particularly microwaves, due
to the same principle by which your (duh) microwave oven works. Tissue
damage occurs because of simple heating of molecules of matter from
the sheer raw power of the RF, not due to any "focusing" of
wavelengths.

The eyes, due to the high water content, are especially susceptible to
such damage.

[Peter Duniho]

"Dennis O'Connor" > wrote in message
...
> Larger is better, however... Look at the dish at Arecibo for example..
> http://www.rainforestsafari.com/observe.html

Radio antennae such as that one use reflection, not refraction, to focus
radio waves. In fact, I'm not aware of a single refractor radio antenna.

> Similarily, a camera lens that works efficiently at lower light levels
will
> be larger in diameter for a given focal length than one that doesn't work
as
> efficiently... i.e., an f:2.8 lens versus an f:1.4 lens..

Larger optical lenses are "faster" (i.e. lower f- number) because they
gather more light. It has nothing to do with wavelengths.

Pete

[Peter Duniho]

"One's Too Many" > wrote in message
om...
> There have been cases of people getting their eyeballs and other body
> parts "cooked" by exposure to strong RF

So?

[Tarver Engineering]

"Teacherjh" > wrote in message
...

>
> Ok, so just what IS a photon?

A photon is a contrivance that has turned out to be unnecessary. (see "In
search of Schrodinger's Kittens")

[Tarver Engineering]

"Tim Witt" > wrote in message
om...
> Jim Weir > wrote in message
>...
> > You kept it out of technobabble, but you kept it far from the truth.
>
> So how about explaining what was untruthful, rather than offering a
> drive-by shooting critique. I read these posts to get smarter not as
> a forum for putdowns.

Mr. Weir gets offended when people post over his head. It is only his way
of expressing his displeasure.

Weir is a big asset to small GA, so he can pretty much express his
displeasure as he pleases.

[Tarver Engineering]

"Peter Duniho" > wrote in message
...
> "Ross Oliver" > wrote in message
> ...
> >
> > Everyone else has focused (!) on wavelength, but no one has mentioned
> > radiated power.
>
> That's because the question was "does my lens focus the radio waves", not
> "is my retina being cooked".

A front silvered mirror will.

[Tarver Engineering]

"Teacherjh" > wrote in message
...
> >>
> So why can't we use high-intensity lights powered by a nuclear reactor
> as a source of space propulsion?
> <<
>
> They can. But the F is small, so you need a lot of t to reach much of a
v, as
> long as you are far enough from a g.
>
> Such systems have only been developed in science fiction however because
we are
> not yet doing enough interstellar travel, and people are uncomfortable
with
> nuclear reactors in space.

Here is something interesting Jose.

Although light is not conducted like RF, light behaves very much like RF in
a wave guide.

[Teacherjh]

>>
Although light is not conducted like RF, light behaves very much like RF in
a wave guide.
>>

In a wave guide appropriate to light frequency, or to radio frequency?

Jose

--
(for Email, make the obvious changes in my address)

[Tarver Engineering]

"Teacherjh" > wrote in message
...
> >>
> Although light is not conducted like RF, light behaves very much like RF
in
> a wave guide.
> >>
>
> In a wave guide appropriate to light frequency, or to radio frequency?

The size of waveguide is frequency dependant, but the EM characteristics of
light require only a difference of scale. Propigation is still a factor for
materials inside a waveguide though. So as to say, insulator materials may
act differenty to light than RF.

[Teacherjh]

>The size of waveguide is frequency dependant...

Then what, new, are you saying? Light is just like RF, just a different F,
therefore a different scale to see the effects. They have already made
antennas that emit light - they are very small, but they work the way radio
antennas work. I'd be surprised if a suitably scaled wave guide (of an
appropriate material) did NOT work with visible light.

I'm also not sure what you mean by:

> Although light is not conducted like RF

Jose


--
(for Email, make the obvious changes in my address)

[Tarver Engineering]

"Teacherjh" > wrote in message
...


Metal is not a conductor of light.

Glass is not a conductor of RF.

[Dennis O'Connor]

Pete old pal, too much caffeine?
Firstly, rf energy does refract as it passes through the near field of a
tuned element/antenna... If it did not, no radio antenna could work - just
think, no MTV, what a shame...
A good place to look for this without a lot of calculus is in Les Moxon's,
G6XN, "HF Antennas For All Locations" <published by the RSGB>... Review the
discussion of Super Gain Antennas for a two element array consisting of a
driven half wave dipole element and a closely coupled parasitic dipole
director... The incoming wave front interacts with the director as it passes
over it, and is bent/refracted, focusing it on the driven element raising
the gain of the antenna in exactly the same manner as a telescopic lens...
John Kraus,W8JK, also has good discussions on this in his tome - Antenna
Engineering Handbook - ...

And you are correct that Arecibo dish is mainly a reflector - which,
interestingly, is simply a special case of refraction - but I was using it
to make the point about gathering power increasing as the diameter of the
antenna in wavelengths, increases - and it is one antenna most non technical
folks are familiar with......

Have a look at Feinman's discussion on the relationship between % of
reflected waves and % of refracted waves as light passes through glass with
two plane parallel surfaces where the distance between the two surfaces is
varied in fractions of a wavelength.. Fascinating... Reflection/refraction
are two sides of the same coin...

And I don't know what to think about your last statement... But let me
point out that the faster lens 'gathers more light' because it has a larger
diameter in wavelengths, compared to the slower lens (assuming same focal
length for both)

cheers ... denny

"Peter Duniho" <> Radio antennae such as that one use reflection, not
refraction, to focus
> radio waves. In fact, I'm not aware of a single refractor radio antenna.

> Larger optical lenses are "faster" (i.e. lower f- number) because they
> gather more light. It has nothing to do with wavelengths.
>
> Pete
>
>

[Dennis O'Connor]

Now you are getting technical... I will be forced to reorient your wave
guide mode discharge if you keep it up...
denny
"Teacherjh" > wrote in message
...
> >>
> radar technicians have accidently had eye damage from looking into a
working
> antenna...
> <<
>
> or even looking away from... as proximity is the only important factor,
not
> orientation.
>
> Jose
>
>
> --
> (for Email, make the obvious changes in my address)

[Teacherjh]

>>
Metal is not a conductor of light.
Glass is not a conductor of RF.
<<

Nothing fundamental here. Glass is not a conductor of UV either. And
distinguish RF radiation (wide light) from RF electric signals (electrons
vibrating quickly, but not as fast as they would need to to transmit LF)

Wavelength dependence. It's what's for dinner.

Jose


--
(for Email, make the obvious changes in my address)

[Tarver Engineering]

"Teacherjh" > wrote in message
...
> >>
> Metal is not a conductor of light.
> Glass is not a conductor of RF.
> <<
>
> Nothing fundamental here.

In fact, from an EM standpoint, that is the answer to the original poster's
question.

An iron nail will "focus" RF.

[David CL Francis]

On Wed, 18 Feb 2004 at 22:16:27 in message
<%uRYb.353608$na.522124@attbi_s04>, Jay Honeck
> wrote:

>I've never heard of anyone frying their retinas by looking at a radio
>transmitter, but this begs the question: Can the lens in your eye focus
>radio waves?

No, Firstly the transparency of materials to EM radiation varies with
frequency. Secondly the wavelength of the transmissions is very large
compared to the lens in your eye. A 3GHz transmission has a wavelength
of 10cm.Red light, the longest wavelength of visible light has a
wavelength of about 1 micron (! millionth of a metre).

E&OE
--
David CL Francis

[Peter Duniho]

"Tarver Engineering" > wrote in message
...
> In fact, from an EM standpoint, that is the answer to the original
poster's
> question.
>
> An iron nail will "focus" RF.

I don't think Jay has iron nails for lenses in his eyes.

However, it wouldn't surprise me to find you have iron nails in your eyes.
It sure would explain a lot.

Jose: I'm not sure if you are just having fun with Tarver, or if you think
he's actually someone seriously worth engaging. If it's the latter,
however, I recommend you Google on his posts before you invest a lot of time
with him.

Pete

[Tarver Engineering]

"Peter Duniho" > wrote in message
...

<snip>
> Jose: I'm not sure if you are just having fun with Tarver, or if you think
> he's actually someone seriously worth engaging. If it's the latter,
> however, I recommend you Google on his posts before you invest a lot of
time
> with him.

Oh my, Peter is really having a meltdown over this thread.

[Peter Duniho]

"Dennis O'Connor" > wrote in message
...
> Pete old pal, too much caffeine?

Huh?

> Firstly, rf energy does refract as it passes through the near field of a
> tuned element/antenna

I never said it didn't.

> And I don't know what to think about your last statement... But let me
> point out that the faster lens 'gathers more light' because it has a
larger
> diameter in wavelengths, compared to the slower lens (assuming same focal
> length for both)

That's just baloney. It gathers more light because of the larger aperture,
letting in more of the incoming light. It has nothing to do with
wavelengths (though, it is certainly true that, a wavelength simply being
one way to measure linear distance, you certainly can measure the lens
aperture in wavelengths, just as easily as in inches, cm, mm, or whatever).

Light spreads out as it travels. At a certain distance, a certain
percentage of the light from a given source is present across a given area.
The percentage is inversely proportional to the distance from the source of
light, and directly proportional to the size of the area. Increase the
area, or decrease the distance, and you get more light. It's a simple
matter of how much light gathering surface you put in front of the light,
and has nothing to do with the relationship between the area and the
wavelength of the incoming light.

The same thing is true of the reflector dishes used for radio astronomy and
other radio reception. Making them larger allows them to gather more of the
radiation being received. It's as simple as the fact that more of the dish
is "in the way" of the incoming radiation. It's no different than how a
bucket with a one foot opening will catch more rain than a glass with a one
inch opening.

Just because wavelength is a distance and diameter is a distance, that
doesn't mean that every effect caused by a change in diameter is directly
related to the radiation's wavelength. Size matters in other ways too.
Introducing wavelengths simply obfuscates the issue.

Pete

[Tarver Engineering]

"Peter Duniho" > wrote in message
...
> "Dennis O'Connor" > wrote in message
> ...
> > Pete old pal, too much caffeine?
>
> Huh?

Duh?

[Jim Fisher]

"Teacherjh" > wrote in message
>people are uncomfortable with > nuclear reactors in space.

Well, uncomfortable with getting them there, actually.

--
Jim Fisher

[Todd Pattist]

"Peter Duniho" > wrote:

>Jose: I'm not sure if you are just having fun with Tarver, or if you think
>he's actually someone seriously worth engaging. If it's the latter,
>however, I recommend you Google on his posts before you invest a lot of time
>with him.
>
>Pete

Jose - In case you want confirmation, Pete's giving you good
advice here.
Todd Pattist
(Remove DONTSPAMME from address to email reply.)
___
Make a commitment to learn something from every flight.
Share what you learn.

[Dennis O'Connor]

I'm not in favor of the term 'conductor', which implies electron flow, in
this discussion, as the electron is a phenomenon not directly responsible
for the principles of refraction/reflection of light...

Actually, metals do respond to light in several ways.. One is the
photoelectric effect <there's your electron flow>... And, thin layers of
metals are coated onto glass surfaces to alter it's refraction/reflection
characteristics to light, so metal can both refract and reflect at light
frequencies, depending upon the bulk state, without depending upon electron
flow...

And glass is too nonspecific a term, as various elements/molecules can be
incorporated into basic soda glass to alter it's transparency to EM energy
at various wavelengths ranging from rf to light and beyond...

The point you make about all material/physical response depending on
wavelength is right on... The only difference between the radio signal from
the local rock station and a gamma ray, is wave length...

Enough QED physics here - I'm off the topic...
denny

> >>
> Metal is not a conductor of light.
> Glass is not a conductor of RF.
> <<
>
> Nothing fundamental here. Glass is not a conductor of UV either. And
> distinguish RF radiation (wide light) from RF electric signals (electrons
> vibrating quickly, but not as fast as they would need to to transmit LF)
>
> Wavelength dependence. It's what's for dinner.
>
> Jose
>
>
> --
> (for Email, make the obvious changes in my address)

[Tom Pappano]

Peter Duniho wrote:
> "Dennis O'Connor" > wrote in message
> ...
>
>>Larger is better, however... Look at the dish at Arecibo for example..
>>http://www.rainforestsafari.com/observe.html
>
>
> Radio antennae such as that one use reflection, not refraction, to focus
> radio waves. In fact, I'm not aware of a single refractor radio antenna.
>

There are indeed refracting antennas. A common type is a dielectric
antenna in the form of a plastic "wedge" shape that protrudes, for
example, from the end of a waveguide. Various vehicular "speed radar"
detectors used antennas like this in years past. Microwave antennas
can also employ solid lenses, made of materials like polystyrene, and
for larger lenses that would be heavy, a matrix of plastic balls
with an overall lens shape serves the same purpose while saving weight.
A convenient material to experiment with for making you own dielectric
antennas is common paraffin wax.

Tom Pappano, PP-ASEL-IA

[Tarver Engineering]

"Todd Pattist" > wrote in message
...
> "Peter Duniho" > wrote:
>
> >Jose: I'm not sure if you are just having fun with Tarver, or if you
think
> >he's actually someone seriously worth engaging. If it's the latter,
> >however, I recommend you Google on his posts before you invest a lot of
time
> >with him.

> Jose - In case you want confirmation, Pete's giving you good
> advice here.

Jose has been posting to me for years.

The difference being, Jose doesn't get his apnties in a wad when he learns
something.

[Jim Weir]

I cannot run the train
I cannot ding the bell
But let it jump the goddamned track
And see who catches hell

(Posted prominently above my engineering bench)

Jim



Nomen Nescio ]>
shared these priceless pearls of wisdom:

-> Face it, nobody likes an engineer.....................until they have a
problem
->that NEEDS to be solved.



Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com

[Tarver Engineering]

"Nomen Nescio" ]> wrote in message
...
> -----BEGIN PGP SIGNED MESSAGE-----
>
> From: "Tarver Engineering" >
>
> >Jose has been posting to me for years.
> >
> >The difference being, Jose doesn't get his apnties in a wad when he
learns
> >something.
>
> There seems to be quite a few "Wads" in this group and, as a rule, they
> HATE engineers. As registered PE's, we're the lowest of the lows.

That is the natural reaction to an engineer by a mechanic.

My uncle owned an electrical contracting company in Texas and he hated PEs.

> The
> "know it alls". I guess we're supposed to forget that we've spent years
> banging our heads on books on dif. eq's, physics, electrical circuit
analysis,
> thermodynamics, fluid mechanics, gas dynamics, chemistry, mechanics of
> materials, and methods of scientific analysis as well as a hundred other
> subjects.

They get the most upset when we point out the paradox one of their newsgroup
concensuses.

> Then we're supposed to defer to someone who read an article
> in "Flying", or worse, "Popular Science".
> Face it, nobody likes an engineer.....................until they have a
problem
> that NEEDS to be solved.
> This should really get me on the "sh*t list" around here.

If FAA had implemented FAA Order 8110.37 (1966) WRT professional engineers a
lot less dead people. FAA has now coppied the NCEES model state law into
their Designee selection process.

[Tom|420]

The below answer is from the top of my knowledge. I haven't especially
studied physics, but I had some interest in the field at school, that is
about 10 years ago.


Jay Honeck wrote:

> Okay, here's a weird one for the group: Radio waves are the same as light
> waves, except they're not in the visible spectrum, right?

Wrong. Light is made of of particules which move in an approximate
straight line. I say approximate, because it's not going perfectly
straight. Light going perfectly straight is called 'laser'. The normal
light is not going perfectly straight, that is why you can see a large
area on the highway during the night.

Radio waves is electricity. Remember the atoms drawing from school? The
center of the atom (nucleus) is made of protons (positive charge) and
neutrons (neutral charge), and electrons (negative charge) circle around
the nucleus. To produce electricity you make the electrons to circle
faster than usual. When electrons are going fast enough they will leave
their nucleus and hit the lectrons of the next atoms, replacing it.
Electricity is the form of energy caused by this electrons activity.
When you understand the basic of electricity (what I stated was the very
basic, the reality is clearly more complex and beyond my understanding)
it becomes obvious that electricity doesn't go straight, but instead in
any direction, as long as the matter can handle it (that is, you can
lock electricity within a copper wire because the surrending matter is
not compatible atomic-wise). For radio waves you simply emit electric
signal directly into the air. Unlike for electricity used as power,
electricity used as radio waves is very light (powerless) but very
controled (the frequency must be very precise for the receptor to be
able to reproduce the original signal).

>
> Here's why it matters: As we were departing from Muscatine, IA today (a
> beautiful day to fly in the Midwest, BTW -- clear and warm) after a great
> lunch, my gaze fell on their on-field VOR transmitter. Focusing closely on
> the "Hershey's Kiss"-shaped structure (with my new glasses -- wow, what a
> difference a new prescription makes!), I wondered aloud if the lens in my
> eye was at that moment focusing powerful radio waves onto my retina.

I wouldn't think that is the case. Lens are designed to focus the light
in a particular way (to compensate for your eyes lacking at doing it as
it should be), and I doubt this would have any effect on radio waves at all.

>
> Mary, a scientist with a strong physics background, was not sure if radio
> waves behaved the same as light waves.
>
> I've never heard of anyone frying their retinas by looking at a radio
> transmitter, but this begs the question: Can the lens in your eye focus
> radio waves?
>
> If not, why not?

Have you even lit a fire with your glasses, concentration light from the
sun onto a sheet of paper? I am not quite sure, but I think this is not
possible. Unlike a magnifying glass, your glasses lens are designed to
focus the light, not concentrate it. I don't wear glasses; when you
stare at the sun do you think it burns you eyes harder with glasses than
without it?

Eventhoug radio waves behave like light, I doubt the glasses wouldn't
have any effect, as I don't think it concentrate the waves, just focus
it, and also because radio waves are very light.

Again I am no physicians. Just my 2¢ here.

Tom :)

[Teacherjh]

>>
Light is made of of particules which move in an approximate
straight line. I say approximate, because it's not going perfectly
straight. [snip] Radio waves is electricity. [snip] [etc]
<<

No. Sorry, that's not how it works. There are previous answers in this
thread, I won't recapitulate, but radio is just "long light waves" and light is
just "very short radio waves". The wavelength makes all the difference.

Jose
("you see, the wired telegraph is just like a very long cat. You're pulling
its tail in New York, and it's mewing in London. Wireless radio is just like
that, except there's no cat.")
--
(for Email, make the obvious changes in my address)

[Dan Luke]

"Jim Fisher" wrote:
> Unfortunately, when it comes to physics the more I think I grasp,
> the less I actually grasp. This is called the Aintcertainty
Principal.

Tee-hee!

Every three or four years I buy one of those "Quantum Mechanics for
Laymen" books. I can cram a dim understanding into my brain, but it
evaporates quicker than 100LL on a hot ramp.
--
Dan
C172RG at BFM
(remove pants to reply by email)

[Dan Luke]

"Peter Duniho" wrote:
> > An iron nail will "focus" RF.
>
> I don't think Jay has iron nails for lenses in his eyes.
>
> However, it wouldn't surprise me to find you have iron
> nails in your eyes. It sure would explain a lot.

Haw! Good one.
--
Dan
C172RG at BFM
(remove pants to reply by email)