Module 2 : Transmission Lines
Lecture 5:  Standing Waves on Transmission Line & Impedance Transformation
  Origin of Backward Wave
In our discussion, the generator is connected to the left end of the line. So a voltage travelling wave moving away (the forward wave) from the generator is understandable. However, one would wonder about the origin of the backward wave. There is no energy source at the right end of the line.
   
The only possibility then is, that the forward wave reaches the right end of the line and does not find correct conditions for transfering the full power to the load impedance. The part of the energy then gets reflected from the load which results into the 'Backward Wave'.
   
The strength of the backward wave then should be related to the load impedance with which the line is terminated.
   
Since the forward wave carrys energy towards the load, we call this wave as the 'Incident Wave'. The backward wave which carrys reflected energy from the load is called the 'Reflected Wave'. We therefore have
   
   
   
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