Definition of Incident, Transmitted and Reflected Pulse:
When a wave or pulse traveling through a medium reaches a boundary with another medium, part of the incident pulse is reflected off the boundary and part of the incident pulse is transmitted across the boundary. The incident pulse is the pulse which is approaching the boundary within the original medium. The reflected pulse is the part of the pulse which has bounced off the boundary and is traveling through the original medium. The transmitted pulse is the part of the pulse which has crossed over the boundary and entered into the new medium.