Wave reflection.

["reinifrosch@xxxxxxxxxx" <reinifrosch@xxxxxxxxxx>]

Hello again !

I just found a good introductory treatment on nearly
reflection-free waves, in the book "Physics of Waves"
by W. C. Elmore and M. A. Heald (Dover, New York, 1969).
In their section 9.1, they show that the WKB (Wentzel, Kramers, 
Brillouin) approximation is reflection-free, and that it is
accurate if  the local wavelength lambda obeys the following 
inequality: 

(d lambda / dx)^2 << 32 pi^2 .     [their equation (9.1.15)]  

The corresponding inequality for the local wave number k is:

k^-4 * (dk / dx)^2 << 8 .

Reinhart Frosch.





Reinhart Frosch,
Dr. phil. nat.,
r. PSI and ETH Zurich,
Sommerhaldenstr. 5B,
CH-5200 Brugg.
Phone: 0041 56 441 77 72.
Mobile: 0041 79 754 30 32.
E-mail: reinifrosch@xxxxxxxxxx .