Cecil Moore wrote:
Gene Fuller wrote:
Cecil Moore wrote:
Yes, signals traveling in opposite directions don't interfere.

This is a distinction with no technical value. Waves in the same
location are subject to the usual rules of linear superposition of the
fields. Whether you want to call this "interference" is simply a
philosophical choice.

Not so. Here's what Eugene Hecht says: "... optical
interference corresponds to the interaction of two
or more [plane] light waves yielding a resultant
irradiance that deviates from the sum of the component
irradiances."

Superposition can occur with or without interference. If
P1 and P2 are the power densities for two plane waves:

Why do you attribute such magic to the word "interference"? Do you think
that Hecht's "interaction" is any different than superposition?

What if the waves are not quite anti-parallel, say at an angle of 179
degrees? Is interference now possible?

Suppose the waves are only 1 degree from parallel. Does that negate the
interference?

Repeating: This is a distinction with no technical value.

73,
Gene
W4SZ