Successive Bounces Shrink by Boundary Coefficients
A successive-bounces-shrink-by-boundary-coefficients ledger treats each traveling wave as multiplied by the boundary coefficient it reaches. The 8 V wave reflecting to 4 V and then returning as -2 V is exact only for the stated ideal load and source coefficients. Real lines add loss, dispersion, connector discontinuities, source/load tolerance, finite rise time, calibration limits, finite precision, and measurement uncertainty.
Each traveling wave is multiplied by the boundary it reaches. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
The load boundary multiplies by its coefficient
The first incoming wave is 8 volts and the load coefficient is 1 over 2, so the outgoing wave is 4 volts.
8⋅21=4
The source boundary multiplies the returning wave
The returning 4 volt wave sees source coefficient -1 over 2, giving -2 volts forward.