Re: Why called diffraction?

["John S. Denker" <jsd@MONMOUTH.COM>]

On 04/24/2003 02:38 PM, Laurent Hodges wrote:
> > We shall try to
> > maintain the convention that interference involves the deliberate
> > production of two or more separate beams and that diffraction occurs
> > naturally when a single wave is limited in some way.  We shall not always
> > succeed in maintaining this convention because some names - the
> > diffraction grating, for example - do not fit in with it and are too well
> > established to change.
>
>
> This is the distinction I've always made in class.  Then when discussing
> the "diffraction grating" I point out that it should really be called an
> "interference grating," and treat it as the N-slit interference pattern
> where N is very large.  I hope this makes it clearer to students than just
> calling it a "diffraction grating" with no comment.

I am not seeing the advantage(s) of such a
definition.  The disadvantages seem overwhelming.

 :-) A diffraction grating is not properly
     diffraction???

 :-) A crystal's Xray diffraction pattern is not
     properly diffraction???

 :-) The anti-reflection interference coating on a
     lens is not properly interference???


The alternative seems intuitive and consistent
with all the established usages I can think of.
Can anybody find a problem with this:
 diffraction is defined to be:
    interference of scattered waves
    (sometimes excluding the trivial case
    of the "zeroth-order" diffracted beam).