|
I've possibly been a little too sarcastic in this thead. I hope no one has been offended, but if they have then I apologise....
The inverse square law refers to the way that the intensity of a propagating wave (among other things) decreases with distance from the wave's source, assuming that the wave is spreading out in three dimensions. Intensity is defined as power per unit area (e.g. Watts per square meter). If you imagine sound or light or radio waves coming from a point and radiating outwards in all directions then the energy emitted at any one moment will occupy an expanding sphere. The surface area of the sphere is proportional to the square of its radius - the total area that the energy is spread out over is proportional to the square of the distance from the source. Thus the intensity of the signal falls off in proportion to the square of the distance from the source: twice as far away and the intensity divides by four, three times as far away and it divides by nine, four times as far away and it divides by sixteen, and so on. That means that if you go from a source that is one centimetre away from your head to one that is two metres away then the intensity of the radiation is reduced by a factor of 40,000. And the transmitter for wireless headphones is far less powerful than a mobile telephone anyway.
|