not sure how complex to go(what grade are you in). basically
electrical to mechanical
electromagnetic-electrical-sound there is probably more but you get the jist.
the fax is first off mechanical (moving cmpts) then to electrical then depending on the fax some sort of signal energy then back to mechanical. the modem is the same as the last part of the fax, I am assuming you haven't done any signal processing in yr 11. That is all your teacher would want.