On Apr 8, 7:09 pm, Cecil Moore wrote:
Keith Dysart wrote:
Do Born and Wolf offer crisp definitions of the boundaries
between coherent, partially coherent, and mutually incoherent?
Or is it a continuum arbitrarily divided into 3 regions for
the purposes of discussion?

The IEEE Dictionary has an interesting definition for
"degree of coherence". Imax means intensity maximum
and Imin means intensity minimum.

Visibility = (Imax-Imin)/(Imax+Imin)

Light is considered "highly coherent" when Visibility
exceeds 0.88 and "partially coherent" when Visibility
is less than 0.88. Incoherent for "very small values"
of Visibility.

This is good; a continuum with high coherence at one end, low
coherence at the other and medium in the middle, and, of course,
since the ends are infinitely small, no such thing as perfect
coherence or "NO" coherence (at least in the real world).

This then takes us back to the original point; there is always
some interference, though it may be small enough that an
engineer does not find it of interest.

....Keith