As a result, the vertical displacement on the \(-x\) side of the boundary must be the same as the vertical displacement on the \(+x\) side of the boundary at every instant: \[\begin{aligned} D_{-x}&=D...As a result, the vertical displacement on the \(-x\) side of the boundary must be the same as the vertical displacement on the \(+x\) side of the boundary at every instant: \[\begin{aligned} D_{-x}&=D_{+x}\quad\text{at $x=0$}\end{aligned}\] The amplitude on the \(+x\) side is equal to the amplitude of the transmitted pulse.
