Quantum reflection amplitude
= Quantum reflection amplitude
{title2=$r=A_{\rm reflected}/A_{\rm incident}$}
A <quantum reflection amplitude> is the complex ratio of the outgoing reflected wave to the incident wave in a chosen scattering convention. In one reflected channel with the same exterior speed, the reflection <probability> is $|r|^2$. Its phase affects <interference> even when its modulus is one; shifting the reference plane changes that phase.