subject: Wireless Charging of Mobile Phones using Micro Waves [print this page] INTRODUCTION INTRODUCTION
THE ELECTROMAGNETIC SPECTRUM
To start with, to know what a spectrum is: when white light is shone through a prism it is separated out into all the colours of the rainbow; this is the visible spectrum. So white light is a mixture of all colours. Black is NOT a colour; it is what you get when all the light is taken away.Some physicists pretend that light consists of tiny particles which they call
photons. They travel at the speed of light (what a surprise). The speed of light is about
300,000,000 meters per second. When they hit something they might bounce off, go right
through or get absorbed. What happens depends a bit on how much energy they have. If
they bounce off something and then go into your eye you will "see" the thing they have
bounced off. Some things like glass and Perspex will let them go through; these materials
are transparent. Black objects absorb the photons so you should not be able to see black
things: you will have to think about this one. These poor old physicists get a little bit
confused when they try to explain why some photons go through a leaf, some are
reflected, and some are absorbed. They say that it is because they have different amounts
of energy.Other physicists pretend that light is made of waves. These physicists measure the length of the waves and this helps them to explain what happens when light hits leaves. The light with the longest wavelength (red) is absorbed by the green stuff (chlorophyll) in the leaves. So is the light with the shortest wavelength (blue). In between these two colours there is green light, this is allowed to pass right through or is reflected. (Indigo and violet have shorter wavelengths than blue light.)Well it is easy to explain some of the properties of light by pretending that it is made of tiny particles called photons and it is easy to explain other properties of light by pretending that it is some kind of wave.The visible spectrum is just one small part of the electromagnetic spectrum. These electromagnetic waves are made up of two parts. The first part is an electric field. The second part is a magnetic field. So that is why they are called electromagnetic waves. The two fields are at right angles to each other.Designation Frequency range
L Band 1 to 2 GHz
S Band 2 to 4 GHz
C Band 4 to 8 GHz
X Band 8 to 12 GHz
Ku Band 12 to 18 GHz
K Band 18 to 26 GHz
Ka Band 26 to 40 GHz
Wireless Charging of Mobile Phones using Micro Waves
