Slinky On Lecture Table - Impedance Mismatch
To show partial reflections and dependence of wave speed on density of the medium.
Long SLINKY with string and masking tape.
A string connects one end of a SLINKY with a point about 3/4 of the way from that end, with the end taped to one end of the lecture table. When the SLINKY is extended it has regions with two different densities, causing two different wave speeds. A wave started at the free end of the SLINKY will experience an impedance change and therefore produce partial reflections at the boundary.