What is the exact difference between wavenumber and propagation constant in an electromagnetic wave propagating in a medium such as a transmission line, cause i am a bit confused. Does it have to do with loss in the medium?
The propegation constant has a real and an imaginary part. One of those is equal to the angular wavenumber, the other is proportional to the absorption coefficient. Which is which (which is the real part and which is the imaginary part) depends on what definition you're using for the term "propegation constant". There is more than one definition in common use.