Transmission line and impedance matching

What you are seeing: a coaxial line of characteristic impedance $Z_0 = 50 \, \Omega$ terminated by a load $Z_L$. The reflection coefficient $\Gamma = (Z_L - Z_0) / (Z_L + Z_0)$ measures the ratio of reflected to incident voltage. At matched load $Z_L = Z_0$ the reflection is zero and all power transfers. At open or short the reflection has magnitude 1 and no power transfers.

Slide $Z_L$ over the resistive range $1 \, \Omega$ to $1000 \, \Omega$. The two indicators show $|\Gamma|$ and VSWR. The animated standing wave on the line illustrates that mismatched impedances produce a visible voltage envelope (interference between forward and reflected waves); matched loads give a uniform amplitude.