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Holes in my knowledge.

SquishyDave

Graduate Poster
S
Joined
May 27, 2003
Messages
1,643
I love phsysics. It's the coolest. But I realise I have some frightening holes in my knowledge. You, my information whores, are going to help me fill up my holes....

Perhaps I shouldn't start asking for favours by calling everyone whores and following up with some pretty bad innuendo huh?

A while ago where I work had a survey done of how strong the EM fields are in the office. To see if there are any problems being caused by strong fields.

I think this is a stupid waste of time and money. My understanding is there are two types of stuff that could be floating around the office because of the electrical stuff. That is magnetic fields, and EM radiation.

Is this right? The magnetic fields are a force, that is they have nothing in them, they are like gravity that just sucks stuff towards it.

The EM spectrum, however, has photons and waves in them. Stuff that falls in the visible spectrum ranging up to x-rays and right down to radio waves. Including microwaves that cook food in the kitchens. These are waves and have amplitudes and frequencies, but are also particles and have photons in them. You get these in the wrong way, and they will kill your dna and make your gums bleed. Get them in the right way, and you can see stuff, or listen to the radio, and cook food.

Is this right? I haven't don't this stuff since College (read highschool for merkins) so I might be getting it all mixed up. If I am right, then there are perfectly harmless photons flying around (but only from the fronts of monitors), and even more harmless accidental electromagents slightly increasing the magnetic field above that in which we are all living anyway?

Am I screwing this up and sounding really stupid? I'm begging you guys, help me out here.
 
a_unique_person said:
Not quite on topic, but, according to Mr Dick Wicks, his magnets will ease pain. They must, otherwise my chemist shop wouldn't sell them.
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Peh, don't get me started on that crap. Magnets don't do ANYTHING to us at all. I've seen frigging frogs exposed to magnetic fields so large they are floating. Surely if the stupidly low level fields in "medical magnets" did anything at all, then that frog would have had a massive overdose, and had some serious problems. Apparently it didn't even notice. Peh I say.
 
Health magnets should be up to 500 gauss. The frog was floating in a 10 Tesla field, and 10,000 gauss = 1 Tesla.

So the frog was getting 200 times the recommended dosage. Take 400 asprin and see what happens eh?

ETA I just read the frog was actually in a 16 Telsa field. I can't even do the maths on that it's so high.
 
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My friend the herpetologist said the frog should be fine. Magnetic fields really don't have any effect on humans, not at the level we can comfortably produce them (and I wouldn't worry about them showing up in your office). And you're right, magnetic fields do no work.

Yeah, you don't want to be inundated by x-rays, gamma rays, or even microwaves at work, but I wouldn't worry about those either. There aren't a lot of sources of those lying around (unless the microwave oven has no door on it). Your computers and cell phones are not emitting radiation that's dangerous to the human body.

So yeah, I'd say your company probably wasted their money (unless they know something you don't know, in which case you might want to work from home until your coworkers start showing signs of whatever it is).
 
SquishyDave said:
Peh, don't get me started on that crap. Magnets don't do ANYTHING to us at all. I've seen frigging frogs exposed to magnetic fields so large they are floating. Surely if the stupidly low level fields in "medical magnets" did anything at all, then that frog would have had a massive overdose, and had some serious problems. Apparently it didn't even notice. Peh I say.
Click to expand...

What do you mean by "Floating"? Is that an expression or literally levitating?
 
Thanks eri. That's what I thought.

Even if you were exposed to microwave radiation, wouldn't you start to feel uncomfortably warm and leave before any harm was done?
 
Squishy Dave,

Since no-one seems to have been prepared to answer your post in a helpful way I will do what I can to help.

Basically, your summary of the nature of magnetism and EM waves/particles is correct.

Any magnetism your survey may find is unlikely to be a health hazard of any sort.

As you state, there are many kinds of EM waves. Some are harmless, others may be harmful if in sufficient strength.

Visible light is clearly not harmful. IF (infra red) is not harmful unless it is of very high intensity - if this were the case you'd know it - the room would be hot!. UV (ultra violet) is only harmful if you spend lots of time bathing in it (=sunbathing). Again, if there was a lot of UV around you would probably notice it. At the extremes of the spectrum there are various frequencies that can be harmful. Microwaves, for example, can be harmful - if they can cook meat then they can cook you. Radio waves clearly arent harmful - if they were we would all be dead by now. There are also X-rays and Gamma rays which wont do you any good in high quantitities. I could go on.


Basically, your task is not completely pointless, if there is the remote possibility that there is a high energy source of harmful EM rays in the neighborhood , it would be meaningful to track this down and remove it. In practice though, the likelihood of the EM radiation in your area being harmful is pretty low. Most of the harmful EM radiation that exists has to be produced artificially. Natural radiation is generally acceptable and the stuff put out by electronic equipment is generally innocuous.


What interests me is : when you have done your survey and have results to show, how confident are you that the recipient if those results will actually know how to interpret them?

Edited to add: While I was writing this, three other posters got in with meaningful comments which negates my first line.
 
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Microwave ovens don't generate heat per se, like infrared radiation. They operate around 2.45 GHz, which is the vibrational frequency of water molecules. As the molecules vibrate, their energy increases, increasing the heat of the substance (your food, or perhaps you, if you leave it open). Other microwave frequencies won't do the same thing - most wireless networks operate on 2.4 GHz (not that different, really) and have no negative effect (that we've noticed so far) on humans. TV's broadcast in the microwaves, and the background radiation left over from the Big Bang can be observed in the microwave part of the spectrum (160.4 GHz).

Physics is cool! :D
 
SquishyDave said:
I love phsysics. It's the coolest. But I realise I have some frightening holes in my knowledge. You, my information whores, are going to help me fill up my holes....

Perhaps I shouldn't start asking for favours by calling everyone whores and following up with some pretty bad innuendo huh?

A while ago where I work had a survey done of how strong the EM fields are in the office. To see if there are any problems being caused by strong fields.

I think this is a stupid waste of time and money. My understanding is there are two types of stuff that could be floating around the office because of the electrical stuff. That is magnetic fields, and EM radiation.

Is this right? The magnetic fields are a force, that is they have nothing in them, they are like gravity that just sucks stuff towards it.

The EM spectrum, however, has photons and waves in them. Stuff that falls in the visible spectrum ranging up to x-rays and right down to radio waves. Including microwaves that cook food in the kitchens. These are waves and have amplitudes and frequencies, but are also particles and have photons in them. You get these in the wrong way, and they will kill your dna and make your gums bleed. Get them in the right way, and you can see stuff, or listen to the radio, and cook food.

Is this right? I haven't don't this stuff since College (read highschool for merkins) so I might be getting it all mixed up. If I am right, then there are perfectly harmless photons flying around (but only from the fronts of monitors), and even more harmless accidental electromagents slightly increasing the magnetic field above that in which we are all living anyway?

Am I screwing this up and sounding really stupid? I'm begging you guys, help me out here.
Click to expand...
Are you sure they were testing this for it's potential harm on you and your coworkers? Is it possible they were testing it because you have some sort of sensitive instrumentation or critical electronic equipment where you work?

There was a neonatal intensive care unit that was having trouble with some of our incubators' readouts malfunctioning, and it turns out that they had an X-ray lab directly below the NICU. The X-rays were no problem--they had shielded walls--but the EM radiation was so strong every time they fired up this X-ray machine that it was scrambling the instrumentation on our incubators.

ETA: We're beholden to strict regulations on the amount of EM radiation our machines leak, because it can affect surrounding hospital equipment, or flight instrumentation in the case of a transport unit.
 
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SquishyDave said:
Thanks eri. That's what I thought.

Even if you were exposed to microwave radiation, wouldn't you start to feel uncomfortably warm and leave before any harm was done?
Click to expand...

Not necessarily. Microwaves will start to coook internal organs that dont always have pain or any other sensation receptors. You could bake your liver without knowing about it.
 
chipmunk stew Why am I suddenly hungry? Anyway, no we have nothing even the slightest bit sensitive to anything. We are a small government department that have no special needs. Our function is to actually determine if some doctors are abusing the Australian medicare system. I just make sure the computers run.

Marker You can cook a liver without the owner being aware? That is so cool. Also, this was done ages ago, and I have the results right in front of me. The whole thing was done because a screen would flicker from the magentic field of another screen, so they got these guys in to (and I am quoting from the documenation) "assess the likelihood of adverse health effects of persons using the relevant workstations"

And now to the findings. The highest readings were obtained at this workstation, and they were a whopping 0.002 milliTesla. You read that right. The rest of the office was measured at 0.0005 milliTesla.

The recommendations said that although it was well below the current exposure guidelines, no definitive 'safe' exposure level has been identified. (the quotes around safe are theirs, not mine. WTF do those quotes mean?) They go on to say the workstation shouldn't be used on a continuous 8 hour basis.

Maybe those quotes around 'safe' mean that if a frog can be exposed to 8 million times the field strength than at that workstation and not suffer for it, then it's probably fine. And they are desperately trying to send us a clue as to what a what waste of money they were in order to alleviate their consciences.

Now I'm even more pissed off about this than I was before I read the report.
 
Squish, a lot of what you said is true, but there are some misunderstandings. A magnetic field (and an electric field too) are carried by photons. Electricity and magnetism are basically the same thing, also known as electromagnetism, or EM. A permantent magnet just has a frequency of zero. When the E/M fields vary back and forth, you get waves. At higher frequencies it's often easier to think of the waves as particles (photons), but they're all both waves and photons.

Marker said:
Microwaves, for example, can be harmful - if they can cook meat then they can cook you. Radio waves clearly arent harmful - if they were we would all be dead by now.
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Psst - Marker, microwaves are radio waves.

Most of the harmful EM radiation that exists has to be produced artificially. Natural radiation is generally acceptable
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This just isn't true. AM radio waves are artificial and harmless, UV rays are natural and harmful.

And what's up with the hard to read font?
 
CurtC said:
Squish, a lot of what you said is true, but there are some misunderstandings. A magnetic field (and an electric field too) are carried by photons. Electricity and magnetism are basically the same thing, also known as electromagnetism, or EM. A permantent magnet just has a frequency of zero. When the E/M fields vary back and forth, you get waves. At higher frequencies it's often easier to think of the waves as particles (photons), but they're all both waves and photons.
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Whoa whoa, back up a step. So a my super strong fridge magnets magnetic field is the same as the gamma radiation leaking from uranium? But just has a frequency of zero? They didn't cover this in college. I'm gonna need some clarification here.

ETA I get the waves and photons bit, always have.
 
Man, and I've been psyched about Thermodynamics this semester. It's gonna be so cool when we get to E-M...
 
The thing to remember about the human body is that it's always got a constant flow of blood. It'd be pretty hard to heat up a part of the body enough to damage it without circulation carrying the heat to the skin to be dumped.

I once saw an example of a steak and a person put in a 300 degree F oven for a few hours, the steak cooked and the human sweated.
 
SquishyDave said:
Whoa whoa, back up a step. So a my super strong fridge magnets magnetic field is the same as the gamma radiation leaking from uranium? But just has a frequency of zero? They didn't cover this in college. I'm gonna need some clarification here.

ETA I get the waves and photons bit, always have.
Click to expand...
Electricity and magnetism are flip sides of the same coin. A moving electric charge creates a magnetic field, and movement of an electric charge within a magnetic field produces a force on the charged particle. That's how motors works.

EM radiation can be viewed as propogating by alternating electric and magnetic fields, with the rate at which the fields vary being proportional to the frequency, or inversely proportional to the wavelength, so you can see that as the frequency drops the wavelength increases and the rate at which the fields alternate gets lower. In the limit at which the frequency becomes zero the wavelength is infinite, the fields stop alternating and you have a static field.
 
CurtC said:
Psst - Marker, microwaves are radio waves.
Click to expand...

Nope. Microwave radiation extends from 10^9 - 10^6 Armstrongs. Radio waves are less than 10^9 Armstongs.

CurtC said:
This just isn't true. AM radio waves are artificial and harmless,
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"AM waves" are just radio waves that have been amplitude modulated. I had already stated that they were harmless. Also, stating that "Most of the harmful EM radiation that exists has to be produced artificially" does not imply that all artificial waves are harmful nor that all harmful waves are artificial. I was aiming at concise generality rather than nit-picking accuracy (although I now find you have dragged me down to that).

CurtC said:
UV rays are natural and harmful.
Click to expand...

Note I said "Most" natural waves (rather than all) and had already given UV waves as an exception.

CurtC said:
And what's up with the hard to read font?
Click to expand...

No idea how that happened
 
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