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Re: Longitudinal E-waves ?



In anisotropic materials normal to the wave front is not in the same
direction as Poynting vector or direction of the energy flow. This can be
seen when sending light prependicularly to surface of the material
where in the materia the optical axis has a general (neither paralle,
neither prependicular to the surface). For wave fronts still Snell's law is
valid, of course with different indeces for two polarizations. But if the
incident angle is zero is also refracted angle zero.
But rays come out from the crystal on different places - i. e. they have
different direction iside the crystal.

In such a crystal two perpendicularities have to be speak about.
To the vawe normal - epsilon E is perpendicular, where epsilon is dielectric
tensor and E is electric field. But E by itself is perpendicular
to the direction of the energy flow. It is also possible that it is vice
versa since I am talking by heart. References are for instance Fowles, Born
and Born etc.

Way of talking used in isotropic materials cannot therfore be used for
anisotropic materials directly.

Regards to all

Mojca Cepic

Dr. Mojca Čepič or Dr. Mojca
Čepič
Jožef Stefan Institute Faculty
of Education
Jamova 39
Kardeljeva pl. 16
1000 Ljubljana 1000
Ljubljana
Slovenia
Slovenia
e-mail: mojca.cepic@ijs.si
tel.: +386 61 17 73 471 +386 61 18
92 200
fax.: +386 61 17 73 716 +386 61 18
92 233