doubt reg transmisssion lines and waveguides

Hi people, ive got a doubt in transmission lines..what happens to the input impedance of the transmission line if the length is made as infinite? could you also provide me some tutorials regading the basics of transmission line...?

thanks in advance...

An infinite transmission line behaves like a load equal to its characteristic impedance,if its 50 ohm line than it can be replaced by a 50 ohm load.