Posted on 01/23/2005 7:05:01 PM PST by aculeus
...ionize inner shell elctrons and gamma rays are involved with nuclear processes. UV is sufficient to knock outer shell electrons out.
For some reason that Model number sounds correct. It was early on in the handheld radar gun days.
For Radiation it only depends on the power density in the field you're exposed to. With radiation the energy shuffles back and forth between the E and H fields. Absorption depends mostly on size, with a given conductance. If the field is due to a transmission line(energy not otherwise radiated) a person in that field would suck more energy from the line as you indicated. High AC magnetic fields result from high currents and wires with large spacial separation. Objects within that field will have induced currents that depend on the conductivity of the object. As the frequency goes up, the conductivity limits the power absorpiton from the lossy transmission line. At high frequencies the limited conductivity supports the voltage for high power absorption from the lossy transmission line.
Please, when referring to RF energy in this sense, call it eletrotromagnetic energy, for that's what it really is as opposed to alpha or beta particles or gamma rays (radiation).
It's not clear above if you're using radiation as a noun or a verb; for electromagnetic energy the 'action' for propagation is referred to as 'radiation'.
I'm pretty sure you just said we agree. In any case, it is typical for safe exposure limits to be expressed in terms of power density at frequencies above 300 MHz or so......below that, it's generally magnetic, though electric field would do just as well if you were referring to free-space.
The practical result is that you can contain an electric field in a metal box, however, the magnetic field requires a much more exotic (and expensive) material, Mu-Metal to contain it.
So....Power transformers often have the potential for exceeding safe magnetic exposure limits while meeting the electric field component.
"...when referring to RF energy in this sense, call it eletrotromagnetic energy."
Then I'd loose the distinction between what was radiated and what is contained in the transmission line field. Gamma rays are EM energy too. I think the limits are implied by the context that's limited to the same frequency EME in the transmission line as what's radiated from the antenna.
Then I'd loose the distinction between what was radiated and what isI think you're doing FAR more damage otherwise; you're going to confuse the hell out of the public and those other lay people that read what you wrote several posts above!
I think an opening paragraph with a sentence is reckless and unclear (esp. to the public):
For Radiation it only depends on the power density in the field you're exposed to.It would be MUCH clearer if written thusly:
"For radiated electromagnetic energy it only depends on the power density in the field you're exposed to."I don't expect you'll grasp this distinction, maybe I'm wrong and you will ...
What we have here is TEMPEST in a teapot.
I get the distinction. I was trying to be short and knew I was being really short. On many occasions, I've had to explain density to folks with science degrees, so...
If you keep the spout closed.
How very true.
Yes, I understand that gammas are emitted from the nucleus wherein shifts in the nuclear structure occur. Some of those can be pretty low energy, in the range of high-energy x-rays. One thing one of my graduate committee members was doing was looking at low-energy gamma sources as replacements for some kinds of x-ray machines. The advantages were lower maintenance costs and collimation for sources that are small in spatial extent. The disadvantages were cost and inability to "turn the source off".
The UV and X ranges overlap, as the X and gamma ranges do. Just for the thread, here's the common classification for UV.
UVA - 400 to 320 nm, suntan, bonds weakened.
UVB - 320 to 290 nm, burn, ozone layer absorbs, bonds broke, or weakened, but no ionization
UVC - 290 to <100 nm, ionizing - First electrons are ionized in this range. Hydrogen at 92nm. Iron at 160nm
The common copper aK X-ray line is ~15 nm.
A running flourescent tube contains a small amount of plasma to conduct. It's partially ionized Hg(~2 micrograms/tube). When the light is turned off, the Hg regains an electron and an ~120nm photon of UVC is emitted. The phosphor and tube absorb that.
UVC lights are sold for air and water sterilizaiton.
Back in the 1950s when the air was clean in somewhat bucolic (at the time) central NJ, I remember my Mom hanging the clothes out on the line (before zoning laws prohibited such stuff) to dry on windy, sunny days. She always said that the wind made them soft and clean-smelling, and the sun sterilized the cloth. Guess it was that UVC component of sunlight doing that.
I'd do it where I live now except we seldom get sunny days, and my wife won't do it anyway (too much like work carrying that basket outside).
I think the UVC gets taken out by the ionosphere. Most of the UVB is taken out by the ozone layer, else I'd have been extra crispy a long time ago. Instead, I'm just rare.
I still use the clothes line. It's not easy to keep things from smelling like dust.
Dusty clothes? I tried to put a dirt-surface basketball hoop near the clothesline but Mom scotched that idea quick. We had a few beetles and bugs to shake out of the sheets when they came in from the lines but not too bad. Kinda fun going out to get those clothes. Nobody seemed to mind my longjohns flapping on the line back then.
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