This simulation shows the behavior of a lossy transmission line (TL). A sinusoidal signal propagates through the TL and, due to the losses, the signal decays when it advances. If you stop the motion at t=8s and join the peaks with an imaginary line, a decreasing exponential can be sketched. Moreover, this TL is not matched. It is very difficult to see the backward wave because it has very low level. However, if you stop the motion at t=10 s, you can see that the waveform at the end of the line is different to the waveform at the beginning.