Explain how a standing wave is set up on a string fixed at both ends.

An oscillation is send down the string which is reflected at the other end. This leads to the superposition of two waves, the transmitted and reflected wave, on the string. At the ends, where reflection occurs, the two waves are 180 degrees out of phase, leading to non-moving points, or nodes. This also occurs at any point along the string where the waves are 180 degrees out of phase. Where the two waves are in phase, the amplitudes add together creating the greatest motion of the string, known as an antinode.