Rayleigh distance

Rayleigh distance

[′rā·lē ‚dis·təns]
(physics)
For electromagnetic, acoustic, or elastic waves emitted from a uniformly excited planar array transmitting a sinusoidal signal, the distance from the array at which there is a transition from a near-field region, in which the radiated energy is confined to a cylindrical region, to a far-field region, in which the wave field exhibits spherical spreading and the field amplitude varies inversely with range.
References in periodicals archive ?
0] is the Rayleigh distance and is defined as a/[lambda] where [lambda] is the acoustic wavelength: