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Type of electromagnetic diffraction
According to the principle of
diffraction
, when a wave front passes an obstruction, it spreads out into the shadowed space. A
creeping wave
in
electromagnetism
or
acoustics
is the wave that is diffracted around the shadowed surface of a smooth body such as a
sphere
.
Creeping waves greatly extend the
ground wave
propagation
of long
wavelength
(low frequency) radio. They also cause both of a person's ears to hear a
sound
, rather than only the ear on the side of the head facing the origin of the
sound
. In
radar
ranging, the creeping wave return appears to come from behind the target.
Vladimir Fock
made important contributions to the understanding and calculation of creeping waves. They are described by
Airy functions
.