Why can water waves and waves on a rope be transverse as well as longitidunal?
Your question does not seem to make sense. When people say “water waves” or “waves on a rope” they are (as far as I know) always talking about transverse waves. Transverse waves are mechanical waves where the displacement of the medium is perpendicular to the direction of wave propagation. Longitudinal waves in water or on a rope are possible, but people would not call them “water waves” or “waves on a rope:” They would be called “sound waves,” and they would propagate at the speed of sound in the medium. You would not be able to see them.
