For a more detailed partition of the electro magnetic spectrum into these bands please see http://en.wikipedia.org/wiki/Radio_spectrum
Low frequency electromagnetic radiation is created around a conductor when an electic current is making its way across it. Therefor most if not all electric appliances will produce a low frequency electromagnetic field around it. If and when the current changes the field will change (in the same frequency). The electric power supply to our homes and cities is "Alternating Current" (AC) in the frequency of 50 to 60Hz (60 cycles per second). Since the electric power supply frequency is around 50 or 60Hz, then most of the low frequency EMF/EMR in our surroundings will also be close to 50 or 60Hz; most but not all. The earth also produces a magnetic field, but the earth's field is a constant fields(DC).
The 2 main facts about low frequency EMR are:
1. It is very hard to block it and sometimes when blocked it will pass around the barrier. The barrier materials are very expensive.
2. It fades away really fast and most of the time the best thing to do in order to stop your exposure to it is to move (or to move it) one meter aside.
Video link: EMF/EMR sources in low frequency
High frequency sources are very common today. In this category falls all electronic communication equipment, mobile phones, mobile phone masts, microwave ovens, wifi routers, wifi laptops, cordless phones, RF transmitters, military equipment, radar and many more devices and sources.
The higher the frequency is the longer the radiation beam can travel in the air, but on the other hand it is easier to block this radiation with common and affordable protection and blocking materials. For example a mobile phone mast antenna can radiate for several kilometers and a simple see through window cover will block it from penetrating your window.
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No Radiation For You" (c) 1/1/2010"