In physics, coherence length is the propagation distance from a coherent source to a point where a wave (e.g. an electromagnetic wave) maintains a specified degree of coherence. Within this distance, the wave in question is most similar to a perfect sinusoidal wave. The significance is that wave interference will be strong within a coherence length of the source, but not beyond it. This concept is also commonly used in telecommunication engineering.
This article focuses on the coherence of classical electromagnetic fields. In quantum mechanics, there is a mathematically analogous concept of the quantum coherence length of a wave function.
Famous quotes containing the words coherence and/or length:
“Art and ideology often interact on each other; but the plain fact is that both spring from a common source. Both draw on human experience to explain mankind to itself; both attempt, in very different ways, to assemble coherence from seemingly unrelated phenomena; both stand guard for us against chaos.”
—Kenneth Tynan (1927–1980)
“Men sometimes speak as if the study of the classics would at length make way for more modern and practical studies; but the adventurous student will always study classics, in whatever language they may be written and however ancient they may be. For what are the classics but the noblest recorded thoughts of man?... We might as well omit to study Nature because she is old.”
—Henry David Thoreau (1817–1862)