Re: [Phys-l] "Unlearning"

[John Denker <jsd@av8n.com>]

At 9:01 AM +0100 9/10/10, Dr. Keith S. Taber wrote:
> > > Can a ray of light really be considered analogous to something with 
> > > a definite broadness as needed
> > > for that analogy to work?


On 09/10/2010 08:24 AM, chuck britton wrote:

> Yes

Agreed.

> Huygen's Model of wavelets has some pretty strong adherents.

And continuing that thought:  This is why we demonstrate
passing a "ray" of light through a "broad" slit and then
through a not-so-broad slit.  It is good to delineate the
boundary between ray optics and wave optics, i.e. between
geometrical optics and physical optics.

It is important for students to see that geometrical
optics _corresponds_ to physical optics in some limits
but not in others.  The _correspondence principle_ is an 
important tool, an important part of the general-purpose
critical-thinking skill set.

IMHO the correspondence principle is far more important
than anything the student might learn about optics _per se_.