Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: dude777 on 02/04/2013 22:41:13

Title: reflecting electromagnetic radiation from a laptop
Post by: dude777 on 02/04/2013 22:41:13
Hello to all the awesome people who make the world go around! I have a question to you guys - how or what material could help me reflect the electromagnetic waves/radiation that my laptop emits?

And what's the science behind it - why does it reflect?

Thank you for your kind answers in advance!

A. 
Title: Re: reflecting electromagnetic radiation from a laptop
Post by: FuzzyUK on 02/04/2013 23:29:19
Hello to all the awesome people who make the world go around! I have a question to you guys - how or what material could help me reflect the electromagnetic waves/radiation that my laptop emits?

And what's the science behind it - why does it reflect?

I have to scratch my head wondering what's going on in the heads of members of the public when they ask questions like this? Are they envisaging in their minds something akin to a nuclear reactor leaking mega doses of dangerous radiation? I'll give an answer as I'm an electronic design engineer but first I'm curious to know what drives you to make such assumptions, where you picked up your fears, and what damage to your health do you think will happen?
Title: Re: reflecting electromagnetic radiation from a laptop
Post by: RD on 03/04/2013 01:27:57
The electromagnetic radiation emitted by a computer is not potentially harmful ionizing radiation (http://en.wikipedia.org/wiki/Ionizing_radiation) ... http://www.thenakedscientists.com/forum/index.php?topic=44351.msg389722#msg389722
Title: Re: reflecting electromagnetic radiation from a laptop
Post by: syhprum on 03/04/2013 07:38:40
the most energetic radiation emitted from your computer is in the one micron infer red range similar in frequency and quantity to that emitted by another human being
Title: Re: reflecting electromagnetic radiation from a laptop
Post by: dude777 on 03/04/2013 08:39:26
But for some reason there are a number of studies which state that EMR is harmful - it reduces fertility, sperm count, currents in human body and so forth.
http://www.huffingtonpost.com/2011/11/29/laptop-wifi-sperm-damage-electromagnetic-radiation_n_1118726.html (http://www.huffingtonpost.com/2011/11/29/laptop-wifi-sperm-damage-electromagnetic-radiation_n_1118726.html)
http://www.defenderpad.com/study-exposes-increased-health-risks-from-laptop-emfs-particularly-during-pregnancy/ (http://www.defenderpad.com/study-exposes-increased-health-risks-from-laptop-emfs-particularly-during-pregnancy/)
But still even if it aint harmful, how could I reflect the electromagnetic waves/radiation anyways?

Thx!
A.
Title: Re: reflecting electromagnetic radiation from a laptop
Post by: lightarrow on 03/04/2013 10:29:19
I have a question to you guys - how or what material could help me reflect the electromagnetic waves/radiation that my laptop emits?
In case, you should have worried when you had a CRT monitor, not now that you have a liquid crystals screen  [:)]
Title: Re: reflecting electromagnetic radiation from a laptop
Post by: evan_au on 03/04/2013 11:46:42
You can reflect the radiation away by making a metal shield (eg aluminium foil), and positioning it between yourself and the source of electromagnetic waves, or wrapping it around the electronic device (being careful not to cover any cooling holes).

But if you look inside nearly all electronic devices, you will find that they already have a metal shield built into the case, to keep in the electromagnetic radiation (it also helps to keep out external sources of ElectroMagnetic Interference=EMI, like mobile phones).

The rationale for the EMI regulations is that someone else's electronic device should not interfere with your enjoyment of AM radio. AM radio is very susceptible to interference, and that makes it a very sensitive detector. Get a battery-powered portable AM radio (there might be in the back of a cupboard, somewhere) and tune it between stations. Move it next to the electronic device, and you will almost certainly hear buzzing and/or hissing noises; changing the tuning a bit lets you hear other buzzes and hisses.

You can use this method to compare the radiation from different electronic devices, and see how far away to put them before the EMI is undetectable; you can put the computer 1 or 2 meters away, and run a cable to the display. The AM radio also shows you how effective any shielding is.

The hardest part to shield is the display and cooling holes - obviously a sheet of aluminium foil defeats the purpose of the airflow and the display! (your mouse and keyboard won't work too well if wrapped entirely in foil, either!) If you look into the fan outlet of your laptop, you will see that it already has a mesh there. I have seen displays with a fine metal mesh built into the CRT screen, and you could try this yourself. But modern LCD displays don't put out too much EMI.
Title: Re: reflecting electromagnetic radiation from a laptop
Post by: yor_on on 03/04/2013 13:44:14
My friend, it's useless worrying :)
there have been so many things potentially harmful in mankinds history, and we're still here, ain't we? And you have worse things to worry about than that if you look around a little. Enjoy your life, it won't be shortened by your computer, and weight that radiation against your mind and knowledge growing, using the Internet. Let's hope it will continue to be free for all.
Title: Re: reflecting electromagnetic radiation from a laptop
Post by: Bored chemist on 03/04/2013 19:28:34
Typical laptop PSUs seem to be rated about at 100W.
100J/s
6000J/min
360,000 J/hr
8,640,000J/day
That's about 2100Kcal per day
On the other hand, I dissipate about 2400 Kcal per day.

So the question should be
"How can I screen my poor laptop from all the radiation I generate?"

(I'm also pretty much guaranteed to be more radioactive than my laptop too)
Title: Re: reflecting electromagnetic radiation from a laptop
Post by: lightarrow on 03/04/2013 19:44:43
My friend, it's useless worrying :)
there have been so many things potentially harmful in mankinds history, and we're still here, ain't we? And you have worse things to worry about than that if you look around a little.
Right. By the way: I would better worry about background natural radiation, instead, included Radon.
Title: Re: reflecting electromagnetic radiation from a laptop
Post by: evan_au on 03/04/2013 21:17:09
A desktop computer is an "accidental" radiator, and the EMI levels are very low (and enforced by regulations).

However, there are "intentional" radiators, where the EMI levels are higher by a factor of a thousand to a million than a desktop computer. To deal with these:
So the biggest health risks are from: