A wave machine is used to demonstrate the behavior of a wave at a boundary. An incident pulse is introduced into the left end of the wave machine. It travels through the more dense medium until it reaches the boundary with a less dense medium. At the boundary, both reflection and transmission occur. The reflected pulse is NOT inverted and of about the same length (though a smaller amplitude) as the incident pulse. The transmitted pulse is longer and faster than the incident and transmitted pulse.
To learn more about the behavior of waves at boundaries, visit The Physics Classroom Tutorial.