| free wave | <radiobiology> A wave (for example, electromagnetic) traveling in a homogeneous infinite medium (no boundary conditions). (09 Oct 1997) |
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| longitudinal wave | <physics> Waves where the variation of the field is partially or totally in the direction of propagation (parallel to wavennumber, k [a vector]). Examples include sound waves and Langmuir waves. Contrasted with transverse waves, where the variation is perpendicular to the direction of propagation, such as light waves. (13 Nov 1997) |