what do you need to konw about modulation?

[TyErd]

what are the essential things you will need to know about modulation and demodulation.

[kenhung123]

Hmm probably the wave that looks like carrier, signal, the components, why photodiode is better than LDR, optical fibre>copper.

[Blakhitman]

I can't for the life of me choose the correct carrier/info signal/modulated wave...I need tips...fast.

[ks04]

Carrier signal is alway high frequency, so it is a sin wave which goes up the most and goes up and down the most (high frequency, low period).
Source signal could be anything, i.e. - it doesn't have to be a sin wave but (normally) has a lower frequency then the carrier wave.
The info signal (or modulated signal) is the addition of the two.

Have a look at the VCAA '09 exam, question 8 of the electronics section shows it well - A is the carrier signal, B is the source signal and c is the modulated signal. - just keep in mind that the source signal does not have to be uniform as it is in the question