Another bunch of Illinformed muppets!!

[supersparky]

most...infact every school i know will have their main line or lines(usualy or fiber) to a server room with the main gear and servers plus tape drives and UPS

then patch panels dotted arround the school linked by usualy a double fiber optic line

then into a switch

linked up to a patch or many patch panels

and then off to the outlets

so yes, lan

very little other than the operating system and programme is stored on the indervidual desktop pcs - they tend to be the lowest spec avaliable whilst the servers will be of a very very high spec, as is the equipment like the switches.

 

[johnny_t]

Crafty...WiFi is Microwave.

They transmit at 2.4GHz, which is firmly at the bottom end of the microwave range.

However it is a frequency that does not vibrate water molecules, like in a microwave and the power is so low as to be negligable.

Just a quick note of pedantry - 2.4GHz is pretty much the same frequency that a microwave oven works at, and is directly in the water absorption band. There is a range of unlicensed , frequencies around there that are set aside for what is known as ISM purposes (Industrial, Scientific and Medical). The reason they are used for Wi-Fi is precisely because they are in this water absorption band, and so it limits their range and doesn't cause one base station to interfere with countless others.

However, none of that diminishes your earlier point. Whilst there is a health risk from high-power microwave radiation, the power from these is definitely on the low side - maybe a watt or two, compared to eight hundred out of your microwave, and are too low to cause any risk to your health (this also applies to mobile phones). If the teacher believes it is affecting his health, I would suggest it is a placebo effect.

No they're not - microwaves are microwaves, and radio waves are radio waves.

Not so fast there - Radio waves applies to all electromagnetic waves. Microwaves are just one of the subsets of Radio waves..

Erm . . . . yeah. Cos WIFI uses microwave technology now . . . . icon_rolleyes.gif

Erm.....yes, it does. Not just now either, it always has.....

 

[tim west]

Agreed the others seem to be confusing the use of frequencies/wavebands as in RF ,UHF to the terminology "Waves" and you were correct to use the term Waves as an all encompassing term. A wave is a waveform so radiowave, microwave etc are all waves.

 

[Big_Spark]

For reference, microwaves are radio frequencies from around 800MHz to 20GHz.

No they're not - microwaves are microwaves, and radio waves are radio waves.

Also, there's no universally accepted strict definition, so it's going to be interesting to see your justification for the use of the word "firmly"...

Softus, your being obtuse, the definition of microwave and radio wave is largely arbatory as the two have frequency ranges that merge. All parts of the electromagnetic spectrum are basically light as far as science is concerned. Electromagnetic radiation can be described in terms of a stream of photons, each traveling in a wave-like pattern, moving at the speed of light and carrying some amount of energy. It is accepted that the only difference between radio waves, visible light, and gamma-rays is the energy of the photons. Radio waves have photons with low energies, microwaves have a little more energy than traditonal radio waves, infrared has still more, then visible, ultraviolet, X-rays, and gamma-rays.

Actually, the amount of energy a photon has makes it sometimes behave more like a wave and sometimes more like a particle. This is called the " wave-particle duality" of light. It is important to understand that Iam not talking about a difference in what light IS, but only in how it behaves. Low energy photons (such as radio) behave more like waves, while higher energy photons (such as X-rays) behave more like particles. This is an important difference for scientists to know when they design detectors and telescopes to try to 'see' EM radiation from very low to very high energies. In fact, scientists choose whichever description of light they need for their study.

The truth is, the electromagnetic spectrum can be expressed in terms of energy, wavelength, or frequency. Each way of thinking about the EM spectrum is related to the others in a precise mathematical way. The relationships are:


the wavelength equals the speed of light divided by the frequency or
lambda = c / nu

Where Lambda = wavelength of the radiation
c= speed of light in a vacuum, and
nu = frequency (hz) of the radiation

and

energy equals Planck's constant times the frequency or
E = h x nu

Where E = energy
h = Plank's constant (equal to 6.626 x E-27 erg-seconds)
nu = frequency (hz) of the radiation

 

[Softus]

No they're not - microwaves are microwaves, and radio waves are radio waves.

Not so fast there - Radio waves applies to all electromagnetic waves. Microwaves are just one of the subsets of Radio waves.

Permit me to disagree.

Whilst I'd agree that the definition of "radio waves" is unclear and ambiguous, the definition of "electromagnetic waves" is neither. To use them interchangeably is to be unclear and ambiguous.

For example, visible light is not within the spectrum of radio waves - not in anyone's wildest dreams.

Clearly, there are international agreements over the terms "radio" and "microwave", for example there is UK legislation that prohibits transmission on certain frequencies without a license. However, the terms have no strict definitions, so it's reasonable to defer to the colloquial usage, whereby radio waves are used for broadcast of data, and microwaves for transmission of power.

Radio is generally accepted as having an upper limit of 1GHz; microwaves are in a non-overlapping range with an upper limit of 100GHz (although some people would say 300GHz).

Of course, anyone may use different definitions, but that person has no right to expect anyone to treat what they say/write as unambiguous.

One particularly confusing area is Wi-Fi, because the frequency is within the microwave range, but the transmission is in the manner of radio, because it is modulated.

 

[Softus]

Softus, your being obtuse, the definition of microwave and radio wave is largely arbatory as the two have frequency ranges that merge.

This should be good - your opening sentence heralds a lecture that is devoid of ambiguity and error. I can hardly wait...

All parts of the electromagnetic spectrum are basically light as far as science is concerned.

Electromagnetic radiation can be described in terms of a stream of photons, each traveling in a wave-like pattern, moving at the speed of light and carrying some amount of energy.

How very illuminating.

It is accepted that the only difference between radio waves, visible light, and gamma-rays is the energy of the photons.

The frequency and wavelength also differ.

Radio waves have photons with low energies, microwaves have a little more energy than traditonal radio waves, infrared has still more, then visible, ultraviolet, X-rays, and gamma-rays.

Presumably this paragraph is for anyone who didn't know what the word "difference" meant.

Actually, the amount of energy a photon has makes it sometimes behave more like a wave and sometimes more like a particle. This is called the " wave-particle duality" of light. It is important to understand that Iam not talking about a difference in what light IS, but only in how it behaves. Low energy photons (such as radio) behave more like waves, while higher energy photons (such as X-rays) behave more like particles. This is an important difference for scientists to know when they design detectors and telescopes to try to 'see' EM radiation from very low to very high energies. In fact, scientists choose whichever description of light they need for their study.

And how is this relevant to the topic?

The truth is, the electromagnetic spectrum can be expressed in terms of energy, wavelength, or frequency. Each way of thinking about the EM spectrum is related to the others in a precise mathematical way. The relationships are:


the wavelength equals the speed of light divided by the frequency or
lambda = c / nu

Where Lambda = wavelength of the radiation
c= speed of light in a vacuum, and
nu = frequency (hz) of the radiation

and

energy equals Planck's constant times the frequency or
E = h x nu

Where E = energy
h = Plank's constant (equal to 6.626 x E-27 erg-seconds)
nu = frequency (hz) of the radiation

I see.

So, just to clarify - is all of this utterly irrelevant detail supposed to be an example of something that isn't obtuse?

 

[mlb3c]

I googled this only because the same "panic" happened over here....errr well I say panic, but not really. I think cell phone sales increased!!!!


http://www.blackwell-synergy.com/links/doi/10.1046/j.1432-0436.2001.670401.x

 

[Big_Spark]

Softus, my post was designed to be deliberatly obtuse, however I was also trying to explain how the EM spectrum works and that arbitrary definitions are sometimes misleading..as you have yourself actually concluded in the post directly below mine.

The "confusion" comes from what scientists refer to and what what the general public refer to and how things merge and overlap in colloquial usage.

 

[JohnD]

Hello, mlb3c , welcome back, have you been away?

 

[Big_Spark]

I googled this only because the same "panic" happened over here....errr well I say panic, but not really. I think cell phone sales increased!!!!


http://www.blackwell-synergy.com/links/doi/10.1046/j.1432-0436.2001.670401.x

And here is a classic example at the end of the link in the quote.

There are several reports which indicate that electromagnetic radiation (such as from mobile phones) at non-thermal levels may elicit a biological effect in target cells or tissues.

How misleading and arbitrary is that. Visible light is a form of electromagnetic radiation, I don't think I have heard anyone accuse it of being cancer causing.

It is wide ranging and sweeping statements like that which help to foster the confusion in colloquial usage. It is surprising how many people do not think of visible light as a form of radiation!

 

[Steve]

Permit me to disagree.

No.

How very illuminating

Behave

You two are getting like ban.

 

[Big_Spark]

You two are getting like ban.

To quote Softus

Permit me to disagree

For my part this "banter" between Softus and I I take with a smile on my face and not seriously, and I hope Softus does the same.

Lets not go there with BAS!!

 

[mlb3c]

Hello, mlb3c , welcome back, have you been away?

not away away....just preoccupied

i have some free time and thought i would toss in my penny's worth

 

[tim west]

For my part this "banter" between Softus and I I take with a smile on my face and not seriously, and I hope Softus does the same.

Lets not go there with BAS!!

To be honest I find Softnuts to be extremely irritating and a bore who does nothing but try to wind people up. Best you can do is ignore him, he's not worth the effort.

 

[baldy01]

How misleading and arbitrary is that. Visible light is a form of electromagnetic radiation, I don't think I have heard anyone accuse it of being cancer causing.

Allow me to disagree. Ultraviolet light is on of the most prevalent causes of skin cancer.

And anyone who thinks electromagnetic radiation in the radio bands is not dangerous should take a look at the health and safety rules for people working on rooftop antenna's.