Radio waves vs light waves

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"

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"

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

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

"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

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)

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"

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

"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.

"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.