I'm sooo nervous...
Can anybody explain information, carrier, signal waves and that please?
what affects them, what they do etc.
plz plz plz i dnt understand any of my teacher's notes 
Wow, well, there is a lot to it but I'll try to explain it in a paragraph or so.
Most information in the world is sent and received as analogue data(fluctuating amplitudes of voltage or so). However, there are problems with
transmitting analogue information. The repeater amplifiers that are used to make up for attenuation along transmission lines also amplifies noise because noise is very similar in form to these analogue signals. The information is swamped by the noise and quality of information is poor. Digital conversion is the remedy as these represent information as only high and low voltages and the regenerator amplifier used to compensate for attenuation only amplifies high and low voltages so small fluctuations(i.e. noise) are not amplified with them. Of course this means, that digital information is more tolerant of noise than analogue information. Also, special codes can be added to digital information to enable the receiver to check and correct errors.
There is however still problems associated with transmitting even this digital information, esp. radiowaves. Only one station will be able to work in an area due to interference from another. The aerials involved in transmission would be very long and inefficient(requiring high energy inputs).
The solution is modulation. In modulation, a high frequency wave known as the carrier wave will have its frequency(FM) or amplitude(AM) altered by the information signal so that the carrier frequency transmits the information. The use of a carrier wave allows different radio stations in the same locality to transmit simultaneously. Each station transmits on a different carrier frequency and consequently the carrier waves do not, in effect, interfere with one another. This is because any one receiver is tuned to the frequency of a particular carrier wave. The receiver then responds to, and gives an output based on, the differences in displacement, or frequency, between the actual waveform and the ‘underlying’ carrier wave. In other words, the receiver recognises the information signal and rejects others.
