Two waves overlap to produce a standing wave on a string. The nodes are points where

1. Standing waves form from two identical waves traveling in opposite directions. 2. At nodes, the two waves always cancel, giving zero amplitude. 3. At antinodes, the waves always add, giving maximum amplitude. 4. Nodes and antinodes alternate at intervals of λ/4 along the string. _Source: syllabus Physics, Ch 14 "Waves", §14.5_