Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: [Phys-L] highway mirage



On 04/09/2014 10:15 AM, Carl Mungan wrote:
I agree that if I treat the wavefront as having a finite extent,
then I can consider the top of the wavefront to do something
different than the bottom, and perhaps that's the explanation.

That's the only explanation I can see. That's the physical
optics explanation. I consider it 100% appropriate for a
physics course.

As others have mentioned, another name for this is Fermat's
principle. FWIW I look at pretty much everything this way.
http://www.feynmanlectures.caltech.edu/II_19.html

As the saying goes, an expert should be able to see things in
more than one way, but I am not seeing any geometrical optics
(ray optics) answer. Maybe it's possible, maybe it's not, but
I reckon it would be a whole lot of trouble, and I'm not getting
paid enough to fuss with it.

In particular, the obvious approach is to divide the graded
index into a thousand layers, and integrate the equation of
motion as the ray crosses from layer to layer, using Snell's
law. I just don't see any way to get the thing to keep turning
after it reaches the horizontal direction.

You know it keeps turning, but the layers won't tell you that.

Can we explain the highway mirage using geometric ray optics alone?
If not, okay, but textbooks certainly give the impression that one
can.

The most abundant element in the world is bogusium (abbreviated
Bs). There is a lot of Bs in the textbooks.