🚀 go-pugleaf

In article <1992Oct1.010445.13988@u.washington.edu> whit@milton.u.washington.edu (John Whitmore) writes:
>In article <1992Sep25.073432.29995@hplb.hpl.hp.com> davids@spira.bri.hp.com (david sixsmith (contractor)) writes:

>>2. What is the mechanism which makes the speed of light lower when travelling
>>in such a medium as opposed to traveling in a vacuum ?
>
>	Entrainment of charge.  Free (or nearly free) charges are
>moving inside the medium in response to the electric excitation,
>so that the energy in the wave is not entirely field energy,
>but includes kinetic energy and binding energy of the charges,
>so that the wave equation is significantly altered.
>	One could (equivalently) note that excitations of the
>charge give rise to a phase-shifted response wave, and the sum
>of the incident wave and the response is a slower-moving
>composite wave.

    I always found it interesting that "The incident wave may therefore 
    be regarded as extinguished at any point within the medium by 
    interference with the dipole field and replaced by another wave with 
    a different velocity (and generally also with a different
    direction) of propagation (Born and Wolf, p. 100)."  So actually, 
    there 'aint' no incident wave inside the medium since the medium
    conspires to identically cancel the incident wave.

                            dale bass
-- 
C. R. Bass                                           crb7q@virginia.edu
Department of Mechanical and Aerospace Engineering
University of Virginia
Charlottesville, Virginia                            (804) 924-7926